九、Mybatis 之反射体系详解

以下完整示例请参考 mybatis 源码：https://github.com/RononoaZoro/customize-mybatis （我学习的时候抄的源码）

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本文从以下几个方面介绍：

• 1、反射简介
• 2、Java 中反射机制 Api
• 3、Mybatis 中对反射的应用

1、反射简介

1.1、反射机制定义

• 反射的概念是由Smith在1982年首次提出的，主要是指程序可以访问、检测和修改其本身状态或行为的一种能力。

• 在 Java 环境中，反射机制允许程序在执行时获取某个类自身的定义信息，如属性和方法等，也可以实现动态创建类的对象、变更属性的内容或执行特定的方法的功能。从而使 Java 具有动态语言的特性，增强了程序的灵活性和可移植性。

1.2、反射机制的作用

• 1）、在运行时判断任意一个对象所属的类型。
• 2）、在运行时构造任意一个类的对象。
• 3）、在运行时判断任意一个类所具有的成员变量和方法。
• 4）、在运行时调用任意一个对象的方法，甚至可以调用private方法。
• 5）、注意：上述功能都是在运行时环境中，而不是在编译时环境中。

2、Java 中反射机制 Api

实现Java反射机制的 API 在 Java.lang.reflect 包下，以下是一些重要的类：

• 1）、Class 类：描述类的信息
• 2）、Filed 类：描述属性的信息
• 3）、Method 类：描述方法的信息
• 4）、Constructor 类：描述构造方法的信息
• 5）、Array 类：提供了动态创建数组及访问数组元素的静态方法。该类中的所有方法都是静态的。

3、Mybatis 中对反射的应用

3.1、利用反射创建默认对象

3.1.1、ObjectFactory

对象工厂接口

package com.luo.ibatis.reflection.factory;

import java.util.List;
import java.util.Properties;

/**
 * @author ：archer
 * @date ：Created in 2021/6/15 15:38
 * @description：对象工厂接口
 * MyBatis uses an ObjectFactory to create all needed new Objects.
 * @modified By：
 */
public interface ObjectFactory {

  /**
   * Sets configuration properties.
   * 设置属性值
   * @param properties configuration properties
   */
  void setProperties(Properties properties);

  /**
   * Creates a new object with default constructor.
   * 使用默认构造方法创建对象
   * @param type Object type
   * @return
   */
  <T> T create(Class<T> type);

  /**
   * Creates a new object with the specified constructor and params.
   * 使用特定的构造方法创建对象
   * @param type Object type
   * @param constructorArgTypes Constructor argument types
   * @param constructorArgs Constructor argument values
   * @return
   */
  <T> T create(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs);
  
  /**
   * Returns true if this object can have a set of other objects.
   * It's main purpose is to support non-java.util.Collection objects like Scala collections.
   * 判断是否是集合
   * 它的主要目的是支持非 java.util.Collection 对象，如 Scala 集合。
   * @param type Object type
   * @return whether it is a collection or not
   * @since 3.1.0
   */
  <T> boolean isCollection(Class<T> type);

}

3.1.2、DefaultObjectFactory

默认工厂实现类

• 主要提供创建一些默认的接口实现（如 List 接口是 ArrayList）

/**
 *    Copyright 2009-2018 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package com.luo.ibatis.reflection.factory;


import com.luo.ibatis.reflection.ReflectionException;

import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.util.*;

/**
 * @author ：archer
 * @date ：Created in 2021/6/15 15:38
 * @description：默认对象工厂类
 * @modified By：
 */
public class DefaultObjectFactory implements ObjectFactory, Serializable {

  private static final long serialVersionUID = -8855120656740914948L;

  @Override
  public <T> T create(Class<T> type) {
    return create(type, null, null);
  }

  @SuppressWarnings("unchecked")
  @Override
  public <T> T create(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
    Class<?> classToCreate = resolveInterface(type);
    // we know types are assignable（可转让的）
    return (T) instantiateClass(classToCreate, constructorArgTypes, constructorArgs);
  }

  @Override
  public void setProperties(Properties properties) {
    // no props for default
  }

  /**
   * 实例化
   * @param type
   * @param constructorArgTypes
   * @param constructorArgs
   * @param 
   * @return
   */
  private  <T> T instantiateClass(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
    try {
      Constructor<T> constructor;
      if (constructorArgTypes == null || constructorArgs == null) {
        constructor = type.getDeclaredConstructor();
        if (!constructor.isAccessible()) {
          constructor.setAccessible(true);
        }
        return constructor.newInstance();
      }
      constructor = type.getDeclaredConstructor(constructorArgTypes.toArray(new Class[constructorArgTypes.size()]));
      if (!constructor.isAccessible()) {
        constructor.setAccessible(true);
      }
      return constructor.newInstance(constructorArgs.toArray(new Object[constructorArgs.size()]));
    } catch (Exception e) {
      StringBuilder argTypes = new StringBuilder();
      if (constructorArgTypes != null && !constructorArgTypes.isEmpty()) {
        for (Class<?> argType : constructorArgTypes) {
          argTypes.append(argType.getSimpleName());
          argTypes.append(",");
        }
        argTypes.deleteCharAt(argTypes.length() - 1); // remove trailing（逗号） ,
      }
      StringBuilder argValues = new StringBuilder();
      if (constructorArgs != null && !constructorArgs.isEmpty()) {
        for (Object argValue : constructorArgs) {
          argValues.append(String.valueOf(argValue));
          argValues.append(",");
        }
        argValues.deleteCharAt(argValues.length() - 1); // remove trailing ,
      }
      throw new ReflectionException("Error instantiating " + type + " with invalid types (" + argTypes + ") or values (" + argValues + "). Cause: " + e, e);
    }
  }

  /**
   * 接口解析
   * @param type
   * @return
   */
  protected Class<?> resolveInterface(Class<?> type) {
    Class<?> classToCreate;
    if (type == List.class || type == Collection.class || type == Iterable.class) {
      classToCreate = ArrayList.class;
    } else if (type == Map.class) {
      classToCreate = HashMap.class;
    } else if (type == SortedSet.class) { // issue #510 Collections Support
      classToCreate = TreeSet.class;
    } else if (type == Set.class) {
      classToCreate = HashSet.class;
    } else {
      classToCreate = type;
    }
    return classToCreate;
  }

  @Override
  public <T> boolean isCollection(Class<T> type) {
    return Collection.class.isAssignableFrom(type);
  }

}

3.1.3、示例

TestClass

package com.luo.ibatis.reflection.factory;

/**
 * TestClass
 *
 * @author Ryan Lamore
 */
public class TestClass {
  String myString;
  Integer myInteger;

  public TestClass(String myString, Integer myInteger) {
    this.myString = myString;
    this.myInteger = myInteger;
  }
}

DefaultObjectFactoryTest

public class DefaultObjectFactoryTest {

  @Test
  public void createClass() throws Exception {
    DefaultObjectFactory defaultObjectFactory = new DefaultObjectFactory();
    TestClass testClass = defaultObjectFactory.create(TestClass.class,
        Arrays.<?>>asList(String.class, Integer.class), Arrays.<Object>asList("foo", 0));

    Assert.assertEquals("myInteger didn't match expected", (Integer) 0, testClass.myInteger);
    Assert.assertEquals("myString didn't match expected", "foo", testClass.myString);
  }
    
  @Test
  public void createArrayList() throws Exception {
    DefaultObjectFactory defaultObjectFactory = new DefaultObjectFactory();
    List list = defaultObjectFactory.create(List.class);
    Assert.assertTrue(" list should be ArrayList", list instanceof ArrayList);

    Collection collection = defaultObjectFactory.create(Collection.class);
    Assert.assertTrue(" collection should be ArrayList", collection instanceof ArrayList);

    Iterable iterable = defaultObjectFactory.create(Iterable.class);
    Assert.assertTrue(" iterable should be ArrayList", iterable instanceof ArrayList);
  }
}

3.2、利用反射描述类信息

3.2.1、ReflectorFactory

• 反射工厂接口
• 缓存以及生成描述类信息的 Reflector 实例

package com.luo.ibatis.reflection;

/**
 * @author ：archer
 * @date ：Created in 2021/6/11 17:42
 * @description：反射工厂接口
 * @modified By：
 */
public interface ReflectorFactory {

    boolean isClassCacheEnabled();

    void setClassCacheEnabled(boolean classCacheEnabled);

    Reflector findForClass(Class<?> type);
}

3.2.2、DefaultReflectorFactory

• ReflectorFactory 的默认实现

package com.luo.ibatis.reflection;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * @author ：archer
 * @date ：Created in 2021/6/11 17:53
 * @description：默认反射工厂类
 * @modified By：
 */
public class DefaultReflectorFactory implements ReflectorFactory {

    private boolean classCacheEnabled = true;
    private final ConcurrentMap<Class<?>, Reflector> reflectorMap = new ConcurrentHashMap<Class<?>, Reflector>();

    public DefaultReflectorFactory() {
    }

    @Override
    public boolean isClassCacheEnabled() {
        return classCacheEnabled;
    }

    @Override
    public void setClassCacheEnabled(boolean classCacheEnabled) {
        this.classCacheEnabled = classCacheEnabled;
    }

    @Override
    public Reflector findForClass(Class<?> type) {
        if (classCacheEnabled) {
            // synchronized (type) removed see issue #461
            Reflector cached = reflectorMap.get(type);
            if (cached == null) {
                cached = new Reflector(type);
                reflectorMap.put(type, cached);
            }
            return cached;
        } else {
            return new Reflector(type);
        }
    }
}

3.2.3、Reflector

• mybatis 反射体系核心类：描述类信息的类

package com.luo.ibatis.reflection;

import com.luo.ibatis.reflection.invoker.GetFieldInvoker;
import com.luo.ibatis.reflection.invoker.Invoker;
import com.luo.ibatis.reflection.invoker.MethodInvoker;
import com.luo.ibatis.reflection.invoker.SetFieldInvoker;
import com.luo.ibatis.reflection.property.PropertyNamer;

import java.lang.reflect.*;
import java.util.*;

/**
 * @author ：archer
 * @date ：Created in 2021/6/11 17:43
 * @description：反射执行器
 * @modified By：
 */
public class Reflector {

    private final Class<?> type;
    private final String[] readablePropertyNames;
    private final String[] writeablePropertyNames;
    private final Map<String, Invoker> setMethods = new HashMap<String, Invoker>();
    private final Map<String, Invoker> getMethods = new HashMap<String, Invoker>();
    private final Map<String, Class<?>> setTypes = new HashMap<String, Class<?>>();
    private final Map<String, Class<?>> getTypes = new HashMap<String, Class<?>>();
    private Constructor<?> defaultConstructor;

    private Map<String, String> caseInsensitivePropertyMap = new HashMap<String, String>();

    public Reflector(Class<?> clazz) {
        type = clazz;
        addDefaultConstructor(clazz);
        addGetMethods(clazz);
        addSetMethods(clazz);
        addFields(clazz);
        readablePropertyNames = getMethods.keySet().toArray(new String[getMethods.keySet().size()]);
        writeablePropertyNames = setMethods.keySet().toArray(new String[setMethods.keySet().size()]);
        for (String propName : readablePropertyNames) {
            caseInsensitivePropertyMap.put(propName.toUpperCase(Locale.ENGLISH), propName);
        }
        for (String propName : writeablePropertyNames) {
            caseInsensitivePropertyMap.put(propName.toUpperCase(Locale.ENGLISH), propName);
        }
    }

    private void addDefaultConstructor(Class<?> clazz) {
        Constructor<?>[] consts = clazz.getDeclaredConstructors();
        for (Constructor<?> constructor : consts) {
            if (constructor.getParameterTypes().length == 0) {
                if (canControlMemberAccessible()) {
                    try {
                        constructor.setAccessible(true);
                    } catch (Exception e) {
                        // Ignored. This is only a final precaution, nothing we can do.
                    }
                }
                if (constructor.isAccessible()) {
                    this.defaultConstructor = constructor;
                }
            }
        }
    }

    private void addGetMethods(Class<?> cls) {
        Map<String, List<Method>> conflictingGetters = new HashMap<String, List<Method>>();
        Method[] methods = getClassMethods(cls);
        for (Method method : methods) {
            if (method.getParameterTypes().length > 0) {
                continue;
            }
            String name = method.getName();
            if ((name.startsWith("get") && name.length() > 3)
                    || (name.startsWith("is") && name.length() > 2)) {
                name = PropertyNamer.methodToProperty(name);
                addMethodConflict(conflictingGetters, name, method);
            }
        }
        resolveGetterConflicts(conflictingGetters);
    }

    private void resolveGetterConflicts(Map<String, List<Method>> conflictingGetters) {
        for (Map.Entry<String, List<Method>> entry : conflictingGetters.entrySet()) {
            Method winner = null;
            String propName = entry.getKey();
            for (Method candidate : entry.getValue()) {
                if (winner == null) {
                    winner = candidate;
                    continue;
                }
                Class<?> winnerType = winner.getReturnType();
                Class<?> candidateType = candidate.getReturnType();
                if (candidateType.equals(winnerType)) {
                    if (!boolean.class.equals(candidateType)) {
                        throw new ReflectionException(
                                "Illegal overloaded getter method with ambiguous type for property "
                                        + propName + " in class " + winner.getDeclaringClass()
                                        + ". This breaks the JavaBeans specification and can cause unpredictable results.");
                    } else if (candidate.getName().startsWith("is")) {
                        winner = candidate;
                    }
                } else if (candidateType.isAssignableFrom(winnerType)) {
                    // OK getter type is descendant （后裔）

                    //是否是自身或超类
                } else if (winnerType.isAssignableFrom(candidateType)) {
                    winner = candidate;
                } else {
                    throw new ReflectionException(
                            "Illegal overloaded getter method with ambiguous type for property "
                                    + propName + " in class " + winner.getDeclaringClass()
                                    + ". This breaks the JavaBeans specification and can cause unpredictable results.");
                }
            }
            addGetMethod(propName, winner);
        }
    }

    private void addGetMethod(String name, Method method) {
        if (isValidPropertyName(name)) {
            getMethods.put(name, new MethodInvoker(method));
            Type returnType = TypeParameterResolver.resolveReturnType(method, type);
            getTypes.put(name, typeToClass(returnType));
        }
    }

    private void addSetMethods(Class<?> cls) {
        Map<String, List<Method>> conflictingSetters = new HashMap<String, List<Method>>();
        Method[] methods = getClassMethods(cls);
        for (Method method : methods) {
            String name = method.getName();
            if (name.startsWith("set") && name.length() > 3) {
                if (method.getParameterTypes().length == 1) {
                    name = PropertyNamer.methodToProperty(name);
                    addMethodConflict(conflictingSetters, name, method);
                }
            }
        }
        resolveSetterConflicts(conflictingSetters);
    }

    private void addMethodConflict(Map<String, List<Method>> conflictingMethods, String name, Method method) {
        List<Method> list = conflictingMethods.get(name);
        if (list == null) {
            list = new ArrayList<Method>();
            conflictingMethods.put(name, list);
        }
        list.add(method);
    }

    private void resolveSetterConflicts(Map<String, List<Method>> conflictingSetters) {
        for (String propName : conflictingSetters.keySet()) {
            List<Method> setters = conflictingSetters.get(propName);
            Class<?> getterType = getTypes.get(propName);
            Method match = null;
            ReflectionException exception = null;
            for (Method setter : setters) {
                Class<?> paramType = setter.getParameterTypes()[0];
                if (paramType.equals(getterType)) {
                    // should be the best match
                    match = setter;
                    break;
                }
                if (exception == null) {
                    try {
                        match = pickBetterSetter(match, setter, propName);
                    } catch (ReflectionException e) {
                        // there could still be the 'best match'
                        match = null;
                        exception = e;
                    }
                }
            }
            if (match == null) {
                throw exception;
            } else {
                addSetMethod(propName, match);
            }
        }
    }

    private Method pickBetterSetter(Method setter1, Method setter2, String property) {
        if (setter1 == null) {
            return setter2;
        }
        Class<?> paramType1 = setter1.getParameterTypes()[0];
        Class<?> paramType2 = setter2.getParameterTypes()[0];
        if (paramType1.isAssignableFrom(paramType2)) {
            return setter2;
        } else if (paramType2.isAssignableFrom(paramType1)) {
            return setter1;
        }
        throw new ReflectionException("Ambiguous setters defined for property '" + property + "' in class '"
                + setter2.getDeclaringClass() + "' with types '" + paramType1.getName() + "' and '"
                + paramType2.getName() + "'.");
    }

    private void addSetMethod(String name, Method method) {
        if (isValidPropertyName(name)) {
            setMethods.put(name, new MethodInvoker(method));
            Type[] paramTypes = TypeParameterResolver.resolveParamTypes(method, type);
            setTypes.put(name, typeToClass(paramTypes[0]));
        }
    }

    private Class<?> typeToClass(Type src) {
        Class<?> result = null;
        if (src instanceof Class) {
            result = (Class<?>) src;
        } else if (src instanceof ParameterizedType) {
            result = (Class<?>) ((ParameterizedType) src).getRawType();
        } else if (src instanceof GenericArrayType) {
            Type componentType = ((GenericArrayType) src).getGenericComponentType();
            if (componentType instanceof Class) {
                result = Array.newInstance((Class<?>) componentType, 0).getClass();
            } else {
                Class<?> componentClass = typeToClass(componentType);
                result = Array.newInstance((Class<?>) componentClass, 0).getClass();
            }
        }
        if (result == null) {
            result = Object.class;
        }
        return result;
    }

    private void addFields(Class<?> clazz) {
        Field[] fields = clazz.getDeclaredFields();
        for (Field field : fields) {
            if (canControlMemberAccessible()) {
                try {
                    field.setAccessible(true);
                } catch (Exception e) {
                    // Ignored. This is only a final precaution, nothing we can do.
                }
            }
            if (field.isAccessible()) {
                if (!setMethods.containsKey(field.getName())) {
                    // issue #379 - removed the check for final because JDK 1.5 allows
                    // modification of final fields through reflection (JSR-133). (JGB)
                    // pr #16 - final static can only be set by the classloader
                    int modifiers = field.getModifiers();
                    if (!(Modifier.isFinal(modifiers) && Modifier.isStatic(modifiers))) {
                        addSetField(field);
                    }
                }
                if (!getMethods.containsKey(field.getName())) {
                    addGetField(field);
                }
            }
        }
        if (clazz.getSuperclass() != null) {
            addFields(clazz.getSuperclass());
        }
    }

    private void addSetField(Field field) {
        if (isValidPropertyName(field.getName())) {
            setMethods.put(field.getName(), new SetFieldInvoker(field));
            Type fieldType = TypeParameterResolver.resolveFieldType(field, type);
            setTypes.put(field.getName(), typeToClass(fieldType));
        }
    }

    private void addGetField(Field field) {
        if (isValidPropertyName(field.getName())) {
            getMethods.put(field.getName(), new GetFieldInvoker(field));
            Type fieldType = TypeParameterResolver.resolveFieldType(field, type);
            getTypes.put(field.getName(), typeToClass(fieldType));
        }
    }

    private boolean isValidPropertyName(String name) {
        return !(name.startsWith("$") || "serialVersionUID".equals(name) || "class".equals(name));
    }

    /*
     * This method returns an array containing all methods
     * declared in this class and any superclass.
     * We use this method, instead of the simpler Class.getMethods(),
     * because we want to look for private methods as well.
     *
     * @param cls The class
     * @return An array containing all methods in this class
     */
    private Method[] getClassMethods(Class<?> cls) {
        Map<String, Method> uniqueMethods = new HashMap<String, Method>();
        Class<?> currentClass = cls;
        while (currentClass != null && currentClass != Object.class) {
            addUniqueMethods(uniqueMethods, currentClass.getDeclaredMethods());

            // we also need to look for interface methods -
            // because the class may be abstract
            Class<?>[] interfaces = currentClass.getInterfaces();
            for (Class<?> anInterface : interfaces) {
                addUniqueMethods(uniqueMethods, anInterface.getMethods());
            }

            currentClass = currentClass.getSuperclass();
        }

        Collection<Method> methods = uniqueMethods.values();

        return methods.toArray(new Method[methods.size()]);
    }

    private void addUniqueMethods(Map<String, Method> uniqueMethods, Method[] methods) {
        for (Method currentMethod : methods) {
            if (!currentMethod.isBridge()) {
                String signature = getSignature(currentMethod);
                // check to see if the method is already known
                // if it is known, then an extended class must have
                // overridden a method
                if (!uniqueMethods.containsKey(signature)) {
                    if (canControlMemberAccessible()) {
                        try {
                            currentMethod.setAccessible(true);
                        } catch (Exception e) {
                            // Ignored. This is only a final precaution, nothing we can do.
                        }
                    }

                    uniqueMethods.put(signature, currentMethod);
                }
            }
        }
    }

    private String getSignature(Method method) {
        StringBuilder sb = new StringBuilder();
        Class<?> returnType = method.getReturnType();
        if (returnType != null) {
            sb.append(returnType.getName()).append('#');
        }
        sb.append(method.getName());
        Class<?>[] parameters = method.getParameterTypes();
        for (int i = 0; i < parameters.length; i++) {
            if (i == 0) {
                sb.append(':');
            } else {
                sb.append(',');
            }
            sb.append(parameters[i].getName());
        }
        return sb.toString();
    }

    /**
     * Checks whether can control member accessible.
     *
     * @return If can control member accessible, it return {@literal true}
     * @since 3.5.0
     */
    public static boolean canControlMemberAccessible() {
        try {
            SecurityManager securityManager = System.getSecurityManager();
            if (null != securityManager) {
                securityManager.checkPermission(new ReflectPermission("suppressAccessChecks"));
            }
        } catch (SecurityException e) {
            return false;
        }
        return true;
    }

    /*
     * Gets the name of the class the instance provides information for
     *
     * @return The class name
     */
    public Class<?> getType() {
        return type;
    }

    public Constructor<?> getDefaultConstructor() {
        if (defaultConstructor != null) {
            return defaultConstructor;
        } else {
            throw new ReflectionException("There is no default constructor for " + type);
        }
    }

    public boolean hasDefaultConstructor() {
        return defaultConstructor != null;
    }

    public Invoker getSetInvoker(String propertyName) {
        Invoker method = setMethods.get(propertyName);
        if (method == null) {
            throw new ReflectionException("There is no setter for property named '" + propertyName + "' in '" + type + "'");
        }
        return method;
    }

    public Invoker getGetInvoker(String propertyName) {
        Invoker method = getMethods.get(propertyName);
        if (method == null) {
            throw new ReflectionException("There is no getter for property named '" + propertyName + "' in '" + type + "'");
        }
        return method;
    }

    /*
     * Gets the type for a property setter
     *
     * @param propertyName - the name of the property
     * @return The Class of the propery setter
     */
    public Class<?> getSetterType(String propertyName) {
        Class<?> clazz = setTypes.get(propertyName);
        if (clazz == null) {
            throw new ReflectionException("There is no setter for property named '" + propertyName + "' in '" + type + "'");
        }
        return clazz;
    }

    /*
     * Gets the type for a property getter
     *
     * @param propertyName - the name of the property
     * @return The Class of the propery getter
     */
    public Class<?> getGetterType(String propertyName) {
        Class<?> clazz = getTypes.get(propertyName);
        if (clazz == null) {
            throw new ReflectionException("There is no getter for property named '" + propertyName + "' in '" + type + "'");
        }
        return clazz;
    }

    /*
     * Gets an array of the readable properties for an object
     *
     * @return The array
     */
    public String[] getGetablePropertyNames() {
        return readablePropertyNames;
    }

    /*
     * Gets an array of the writeable properties for an object
     *
     * @return The array
     */
    public String[] getSetablePropertyNames() {
        return writeablePropertyNames;
    }

    /*
     * Check to see if a class has a writeable property by name
     *
     * @param propertyName - the name of the property to check
     * @return True if the object has a writeable property by the name
     */
    public boolean hasSetter(String propertyName) {
        return setMethods.keySet().contains(propertyName);
    }

    /*
     * Check to see if a class has a readable property by name
     *
     * @param propertyName - the name of the property to check
     * @return True if the object has a readable property by the name
     */
    public boolean hasGetter(String propertyName) {
        return getMethods.keySet().contains(propertyName);
    }

    public String findPropertyName(String name) {
        return caseInsensitivePropertyMap.get(name.toUpperCase(Locale.ENGLISH));
    }
}

3.2.4、MetaClass

• 获取类相关的信息

package com.luo.ibatis.reflection;

import com.luo.ibatis.reflection.invoker.GetFieldInvoker;
import com.luo.ibatis.reflection.invoker.Invoker;
import com.luo.ibatis.reflection.invoker.MethodInvoker;
import com.luo.ibatis.reflection.property.PropertyTokenizer;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Collection;

/**
 * @author ：archer
 * @date ：Created in 2021/6/15 15:38
 * @description： 类的元信息
 * @modified By：
 */
public class MetaClass {

    private final ReflectorFactory reflectorFactory;
    private final Reflector reflector;

    private MetaClass(Class<?> type, ReflectorFactory reflectorFactory) {
        this.reflectorFactory = reflectorFactory;
        this.reflector = reflectorFactory.findForClass(type);
    }

    public static MetaClass forClass(Class<?> type, ReflectorFactory reflectorFactory) {
        return new MetaClass(type, reflectorFactory);
    }

    public MetaClass metaClassForProperty(String name) {
        Class<?> propType = reflector.getGetterType(name);
        return MetaClass.forClass(propType, reflectorFactory);
    }

    public String findProperty(String name) {
        StringBuilder prop = buildProperty(name, new StringBuilder());
        return prop.length() > 0 ? prop.toString() : null;
    }

    public String findProperty(String name, boolean useCamelCaseMapping) {
        if (useCamelCaseMapping) {
            name = name.replace("_", "");
        }
        return findProperty(name);
    }

    public String[] getGetterNames() {
        return reflector.getGetablePropertyNames();
    }

    public String[] getSetterNames() {
        return reflector.getSetablePropertyNames();
    }

    public Class<?> getSetterType(String name) {
        PropertyTokenizer prop = new PropertyTokenizer(name);
        if (prop.hasNext()) {
            MetaClass metaProp = metaClassForProperty(prop.getName());
            return metaProp.getSetterType(prop.getChildren());
        } else {
            return reflector.getSetterType(prop.getName());
        }
    }

    public Class<?> getGetterType(String name) {
        PropertyTokenizer prop = new PropertyTokenizer(name);
        if (prop.hasNext()) {
            MetaClass metaProp = metaClassForProperty(prop);
            return metaProp.getGetterType(prop.getChildren());
        }
        // issue #506. Resolve the type inside a Collection Object
        return getGetterType(prop);
    }

    private MetaClass metaClassForProperty(PropertyTokenizer prop) {
        Class<?> propType = getGetterType(prop);
        return MetaClass.forClass(propType, reflectorFactory);
    }

    private Class<?> getGetterType(PropertyTokenizer prop) {
        Class<?> type = reflector.getGetterType(prop.getName());
        if (prop.getIndex() != null && Collection.class.isAssignableFrom(type)) {
            Type returnType = getGenericGetterType(prop.getName());
            if (returnType instanceof ParameterizedType) {
                Type[] actualTypeArguments = ((ParameterizedType) returnType).getActualTypeArguments();
                if (actualTypeArguments != null && actualTypeArguments.length == 1) {
                    returnType = actualTypeArguments[0];
                    if (returnType instanceof Class) {
                        type = (Class<?>) returnType;
                    } else if (returnType instanceof ParameterizedType) {
                        type = (Class<?>) ((ParameterizedType) returnType).getRawType();
                    }
                }
            }
        }
        return type;
    }

    private Type getGenericGetterType(String propertyName) {
        try {
            Invoker invoker = reflector.getGetInvoker(propertyName);
            if (invoker instanceof MethodInvoker) {
                Field _method = MethodInvoker.class.getDeclaredField("method");
                _method.setAccessible(true);
                Method method = (Method) _method.get(invoker);
                return TypeParameterResolver.resolveReturnType(method, reflector.getType());
            } else if (invoker instanceof GetFieldInvoker) {
                Field _field = GetFieldInvoker.class.getDeclaredField("field");
                _field.setAccessible(true);
                Field field = (Field) _field.get(invoker);
                return TypeParameterResolver.resolveFieldType(field, reflector.getType());
            }
        } catch (NoSuchFieldException e) {
        } catch (IllegalAccessException e) {
        }
        return null;
    }

    public boolean hasSetter(String name) {
        PropertyTokenizer prop = new PropertyTokenizer(name);
        if (prop.hasNext()) {
            if (reflector.hasSetter(prop.getName())) {
                MetaClass metaProp = metaClassForProperty(prop.getName());
                return metaProp.hasSetter(prop.getChildren());
            } else {
                return false;
            }
        } else {
            return reflector.hasSetter(prop.getName());
        }
    }

    public boolean hasGetter(String name) {
        PropertyTokenizer prop = new PropertyTokenizer(name);
        if (prop.hasNext()) {
            if (reflector.hasGetter(prop.getName())) {
                MetaClass metaProp = metaClassForProperty(prop);
                return metaProp.hasGetter(prop.getChildren());
            } else {
                return false;
            }
        } else {
            return reflector.hasGetter(prop.getName());
        }
    }

    public Invoker getGetInvoker(String name) {
        return reflector.getGetInvoker(name);
    }

    public Invoker getSetInvoker(String name) {
        return reflector.getSetInvoker(name);
    }

    private StringBuilder buildProperty(String name, StringBuilder builder) {
        PropertyTokenizer prop = new PropertyTokenizer(name);
        if (prop.hasNext()) {
            String propertyName = reflector.findPropertyName(prop.getName());
            if (propertyName != null) {
                builder.append(propertyName);
                builder.append(".");
                MetaClass metaProp = metaClassForProperty(propertyName);
                metaProp.buildProperty(prop.getChildren(), builder);
            }
        } else {
            String propertyName = reflector.findPropertyName(name);
            if (propertyName != null) {
                builder.append(propertyName);
            }
        }
        return builder;
    }

    public boolean hasDefaultConstructor() {
        return reflector.hasDefaultConstructor();
    }
}

3.2.5、MetaObject

• 获取和设置对象的属性值

package com.luo.ibatis.reflection;

import com.luo.ibatis.reflection.factory.ObjectFactory;
import com.luo.ibatis.reflection.property.PropertyTokenizer;
import com.luo.ibatis.reflection.wrapper.*;

import java.util.Collection;
import java.util.List;
import java.util.Map;

/**
 * @author ：archer
 * @date ：Created in 2021/6/15 15:53
 * @description： 对象的元信息
 * @modified By：
 */
public class MetaObject {

    private final Object originalObject;
    private final ObjectWrapper objectWrapper;
    private final ObjectFactory objectFactory;
    private final ObjectWrapperFactory objectWrapperFactory;
    private final ReflectorFactory reflectorFactory;

    private MetaObject(Object object, ObjectFactory objectFactory, ObjectWrapperFactory objectWrapperFactory, ReflectorFactory reflectorFactory) {
        this.originalObject = object;
        this.objectFactory = objectFactory;
        this.objectWrapperFactory = objectWrapperFactory;
        this.reflectorFactory = reflectorFactory;

        if (object instanceof ObjectWrapper) {
            this.objectWrapper = (ObjectWrapper) object;
        } else if (objectWrapperFactory.hasWrapperFor(object)) {
            this.objectWrapper = objectWrapperFactory.getWrapperFor(this, object);
        } else if (object instanceof Map) {
            this.objectWrapper = new MapWrapper(this, (Map) object);
        } else if (object instanceof Collection) {
            this.objectWrapper = new CollectionWrapper(this, (Collection) object);
        } else {
            this.objectWrapper = new BeanWrapper(this, object);
        }
    }

    public static MetaObject forObject(Object object, ObjectFactory objectFactory, ObjectWrapperFactory objectWrapperFactory, ReflectorFactory reflectorFactory) {
        if (object == null) {
            return SystemMetaObject.NULL_META_OBJECT;
        } else {
            return new MetaObject(object, objectFactory, objectWrapperFactory, reflectorFactory);
        }
    }

    public ObjectFactory getObjectFactory() {
        return objectFactory;
    }

    public ObjectWrapperFactory getObjectWrapperFactory() {
        return objectWrapperFactory;
    }

    public ReflectorFactory getReflectorFactory() {
        return reflectorFactory;
    }

    public Object getOriginalObject() {
        return originalObject;
    }

    public String findProperty(String propName, boolean useCamelCaseMapping) {
        return objectWrapper.findProperty(propName, useCamelCaseMapping);
    }

    public String[] getGetterNames() {
        return objectWrapper.getGetterNames();
    }

    public String[] getSetterNames() {
        return objectWrapper.getSetterNames();
    }

    public Class<?> getSetterType(String name) {
        return objectWrapper.getSetterType(name);
    }

    public Class<?> getGetterType(String name) {
        return objectWrapper.getGetterType(name);
    }

    public boolean hasSetter(String name) {
        return objectWrapper.hasSetter(name);
    }

    public boolean hasGetter(String name) {
        return objectWrapper.hasGetter(name);
    }

    public Object getValue(String name) {
        PropertyTokenizer prop = new PropertyTokenizer(name);
        if (prop.hasNext()) {
            MetaObject metaValue = metaObjectForProperty(prop.getIndexedName());
            if (metaValue == SystemMetaObject.NULL_META_OBJECT) {
                return null;
            } else {
                return metaValue.getValue(prop.getChildren());
            }
        } else {
            return objectWrapper.get(prop);
        }
    }

    public void setValue(String name, Object value) {
        PropertyTokenizer prop = new PropertyTokenizer(name);
        if (prop.hasNext()) {
            MetaObject metaValue = metaObjectForProperty(prop.getIndexedName());
            if (metaValue == SystemMetaObject.NULL_META_OBJECT) {
                if (value == null && prop.getChildren() != null) {
                    // don't instantiate child path if value is null
                    return;
                } else {
                    metaValue = objectWrapper.instantiatePropertyValue(name, prop, objectFactory);
                }
            }
            metaValue.setValue(prop.getChildren(), value);
        } else {
            objectWrapper.set(prop, value);
        }
    }

    public MetaObject metaObjectForProperty(String name) {
        Object value = getValue(name);
        return MetaObject.forObject(value, objectFactory, objectWrapperFactory, reflectorFactory);
    }

    public ObjectWrapper getObjectWrapper() {
        return objectWrapper;
    }

    public boolean isCollection() {
        return objectWrapper.isCollection();
    }

    public void add(Object element) {
        objectWrapper.add(element);
    }

    public <E> void addAll(List<E> list) {
        objectWrapper.addAll(list);
    }
}

3.2.6、PropertyCopier

• 类似于 BeanUtils#copyProperties
• 对象属性拷贝：把两个对象中有相同类型和名称的属性，进行属性值的复制

package com.luo.ibatis.reflection.property;

import java.lang.reflect.Field;

/**
 * @author Clinton Begin
 * 属性复制器
 */
public final class PropertyCopier {

  private PropertyCopier() {
    // Prevent Instantiation of Static Class
  }

  public static void copyBeanProperties(Class<?> type, Object sourceBean, Object destinationBean) {
    Class<?> parent = type;
    while (parent != null) {
      final Field[] fields = parent.getDeclaredFields();
      for(Field field : fields) {
        try {
          field.setAccessible(true);
          field.set(destinationBean, field.get(sourceBean));
        } catch (Exception e) {
          // Nothing useful to do, will only fail on final fields, which will be ignored.
        }
      }
      parent = parent.getSuperclass();
    }
  }

}

3.2.7、PropertyNamer

• 属性相关的操作

package com.luo.ibatis.reflection.property;

import com.luo.ibatis.reflection.ReflectionException;

import java.util.Locale;

/**
 * @author ：archer
 * @date ：Created in 2021/6/11 17:47
 * @description：
 * @modified By：
 */
public class PropertyNamer {

    private PropertyNamer() {
        // Prevent Instantiation of Static Class
    }

    public static String methodToProperty(String name) {
        if (name.startsWith("is")) {
            name = name.substring(2);
        } else if (name.startsWith("get") || name.startsWith("set")) {
            name = name.substring(3);
        } else {
            throw new ReflectionException("Error parsing property name '" + name + "'.  Didn't start with 'is', 'get' or 'set'.");
        }

        if (name.length() == 1 || (name.length() > 1 && !Character.isUpperCase(name.charAt(1)))) {
            name = name.substring(0, 1).toLowerCase(Locale.ENGLISH) + name.substring(1);
        }

        return name;
    }

    public static boolean isProperty(String name) {
        return name.startsWith("get") || name.startsWith("set") || name.startsWith("is");
    }

    public static boolean isGetter(String name) {
        return name.startsWith("get") || name.startsWith("is");
    }

    public static boolean isSetter(String name) {
        return name.startsWith("set");
    }
}

3.2.8、PropertyTokenizer

• mybatis 自定义的属性赋值相关的语法

package com.luo.ibatis.reflection.property;

import java.util.Iterator;

/**
 * @author ：archer
 * @date ：Created in 2021/6/15 15:39
 * @description：
 * @modified By：
 */
public class PropertyTokenizer implements Iterator<PropertyTokenizer> {

    private String name;
    private final String indexedName;
    private String index;
    private final String children;

    public PropertyTokenizer(String fullname) {
        int delim = fullname.indexOf('.');
        if (delim > -1) {
            name = fullname.substring(0, delim);
            children = fullname.substring(delim + 1);
        } else {
            name = fullname;
            children = null;
        }
        indexedName = name;
        delim = name.indexOf('[');
        if (delim > -1) {
            index = name.substring(delim + 1, name.length() - 1);
            name = name.substring(0, delim);
        }
    }

    public String getName() {
        return name;
    }

    public String getIndex() {
        return index;
    }

    public String getIndexedName() {
        return indexedName;
    }

    public String getChildren() {
        return children;
    }

    @Override
    public boolean hasNext() {
        return children != null;
    }

    @Override
    public PropertyTokenizer next() {
        return new PropertyTokenizer(children);
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("Remove is not supported, as it has no meaning in the context of properties.");
    }
}

3.2.9、演示示例一：ReflectorTest

package com.luo.ibatis.reflection;

import org.junit.Assert;
import org.junit.Test;

import java.io.Serializable;
import java.util.List;

import static com.googlecode.catchexception.apis.BDDCatchException.caughtException;
import static com.googlecode.catchexception.apis.BDDCatchException.when;
import static org.assertj.core.api.BDDAssertions.then;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

public class ReflectorTest {

  @Test
  public void testGetSetterType() throws Exception {
    ReflectorFactory reflectorFactory = new DefaultReflectorFactory();
    Reflector reflector = reflectorFactory.findForClass(Section.class);
    Assert.assertEquals(Long.class, reflector.getSetterType("id"));
  }

  @Test
  public void testGetGetterType() throws Exception {
    ReflectorFactory reflectorFactory = new DefaultReflectorFactory();
    Reflector reflector = reflectorFactory.findForClass(Section.class);
    Assert.assertEquals(Long.class, reflector.getGetterType("id"));
  }

  @Test
  public void shouldNotGetClass() throws Exception {
    ReflectorFactory reflectorFactory = new DefaultReflectorFactory();
    Reflector reflector = reflectorFactory.findForClass(Section.class);
    Assert.assertFalse(reflector.hasGetter("class"));
  }

  static interface Entity<T> {
    T getId();
    void setId(T id);
  }

  static abstract class AbstractEntity implements Entity<Long> {

    private Long id;

    @Override
    public Long getId() {
      return id;
    }

    @Override
    public void setId(Long id) {
      this.id = id;
    }
  }

  static class Section extends AbstractEntity implements Entity<Long> {
  }
}

3.2.10、演示示例二：MetaObjectTest

RichType

package com.luo.ibatis.domain.misc;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class RichType {

  private RichType richType;

  private String richField;

  private String richProperty;

  private Map richMap = new HashMap();

  private List richList = new ArrayList() {
    {
      add("bar");
    }
  };

  public RichType getRichType() {
    return richType;
  }

  public void setRichType(RichType richType) {
    this.richType = richType;
  }

  public String getRichProperty() {
    return richProperty;
  }

  public void setRichProperty(String richProperty) {
    this.richProperty = richProperty;
  }

  public List getRichList() {
    return richList;
  }

  public void setRichList(List richList) {
    this.richList = richList;
  }

  public Map getRichMap() {
    return richMap;
  }

  public void setRichMap(Map richMap) {
    this.richMap = richMap;
  }
}

MetaObjectTest

package com.luo.ibatis.reflection;

import com.luo.ibatis.domain.blog.Author;
import com.luo.ibatis.domain.blog.Section;
import com.luo.ibatis.domain.misc.CustomBeanWrapper;
import com.luo.ibatis.domain.misc.CustomBeanWrapperFactory;
import com.luo.ibatis.domain.misc.RichType;
import org.junit.Test;

import java.util.*;

import static org.junit.Assert.*;

public class MetaObjectTest {

  @Test
  public void shouldGetAndSetField() {
    RichType rich = new RichType();
    MetaObject meta = SystemMetaObject.forObject(rich);
    meta.setValue("richField", "foo");
    assertEquals("foo", meta.getValue("richField"));
  }

  @Test
  public void shouldGetAndSetNestedField() {
    RichType rich = new RichType();
    MetaObject meta = SystemMetaObject.forObject(rich);
    meta.setValue("richType.richField", "foo");
    assertEquals("foo", meta.getValue("richType.richField"));
  }
}

3.2.11、演示示例三 MetaClassTest

package com.luo.ibatis.reflection;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.luo.ibatis.domain.misc.RichType;
import com.luo.ibatis.domain.misc.generics.GenericConcrete;
import org.junit.Test;

public class MetaClassTest {

  private RichType rich = new RichType();
  Map<String,RichType> map = new HashMap<String,RichType>() {
    {
      put("richType", rich);
    }
  };

  public MetaClassTest() {
    rich.setRichType(new RichType());
  }

  @Test
  public void shouldTestDataTypeOfGenericMethod() {
    ReflectorFactory reflectorFactory = new DefaultReflectorFactory();
    MetaClass meta = MetaClass.forClass(GenericConcrete.class, reflectorFactory);
    assertEquals(Long.class, meta.getGetterType("id"));
    assertEquals(Long.class, meta.getSetterType("id"));
  }

  @Test
  public void shouldCheckGetterExistance() {
    ReflectorFactory reflectorFactory = new DefaultReflectorFactory();
    MetaClass meta = MetaClass.forClass(RichType.class, reflectorFactory);
    assertTrue(meta.hasGetter("richField"));
    assertTrue(meta.hasGetter("richProperty"));
    assertTrue(meta.hasGetter("richList"));
    assertTrue(meta.hasGetter("richMap"));
    assertTrue(meta.hasGetter("richList[0]"));

    assertTrue(meta.hasGetter("richType"));
    assertTrue(meta.hasGetter("richType.richField"));
    assertTrue(meta.hasGetter("richType.richProperty"));
    assertTrue(meta.hasGetter("richType.richList"));
    assertTrue(meta.hasGetter("richType.richMap"));
    assertTrue(meta.hasGetter("richType.richList[0]"));

    assertEquals("richType.richProperty", meta.findProperty("richType.richProperty", false));

    assertFalse(meta.hasGetter("[0]"));
  }
}

3.3、类型解析器:TypeParameterResolver

• 用于解析类型：对泛型的解析很完整，值得参考

package com.luo.ibatis.reflection;

import java.lang.reflect.*;
import java.util.Arrays;

/**
 * @author ：archer
 * @date ：Created in 2021/6/11 17:52
 * @description： 类型参数解析器
 * @modified By：
 */
public class TypeParameterResolver {

    /**
     * @return The field type as {@link Type}. If it has type parameters in the declaration,

     *         they will be resolved to the actual runtime {@link Type}s.
     */
    public static Type resolveFieldType(Field field, Type srcType) {
        Type fieldType = field.getGenericType();
        Class<?> declaringClass = field.getDeclaringClass();
        return resolveType(fieldType, srcType, declaringClass);
    }

    /**
     * @return The return type of the method as {@link Type}. If it has type parameters in the declaration,

     *         they will be resolved to the actual runtime {@link Type}s.
     */
    public static Type resolveReturnType(Method method, Type srcType) {
        Type returnType = method.getGenericReturnType();
        Class<?> declaringClass = method.getDeclaringClass();
        return resolveType(returnType, srcType, declaringClass);
    }

    /**
     * @return The parameter types of the method as an array of {@link Type}s. If they have type parameters in the declaration,

     *         they will be resolved to the actual runtime {@link Type}s.
     */
    public static Type[] resolveParamTypes(Method method, Type srcType) {
        Type[] paramTypes = method.getGenericParameterTypes();
        Class<?> declaringClass = method.getDeclaringClass();
        Type[] result = new Type[paramTypes.length];
        for (int i = 0; i < paramTypes.length; i++) {
            result[i] = resolveType(paramTypes[i], srcType, declaringClass);
        }
        return result;
    }

    private static Type resolveType(Type type, Type srcType, Class<?> declaringClass) {
        if (type instanceof TypeVariable) {
            return resolveTypeVar((TypeVariable<?>) type, srcType, declaringClass);
        } else if (type instanceof ParameterizedType) {
            return resolveParameterizedType((ParameterizedType) type, srcType, declaringClass);
        } else if (type instanceof GenericArrayType) {
            return resolveGenericArrayType((GenericArrayType) type, srcType, declaringClass);
        } else {
            return type;
        }
    }

    private static Type resolveGenericArrayType(GenericArrayType genericArrayType, Type srcType, Class<?> declaringClass) {
        Type componentType = genericArrayType.getGenericComponentType();
        Type resolvedComponentType = null;
        if (componentType instanceof TypeVariable) {
            resolvedComponentType = resolveTypeVar((TypeVariable<?>) componentType, srcType, declaringClass);
        } else if (componentType instanceof GenericArrayType) {
            resolvedComponentType = resolveGenericArrayType((GenericArrayType) componentType, srcType, declaringClass);
        } else if (componentType instanceof ParameterizedType) {
            resolvedComponentType = resolveParameterizedType((ParameterizedType) componentType, srcType, declaringClass);
        }
        if (resolvedComponentType instanceof Class) {
            return Array.newInstance((Class<?>) resolvedComponentType, 0).getClass();
        } else {
            return new GenericArrayTypeImpl(resolvedComponentType);
        }
    }

    private static ParameterizedType resolveParameterizedType(ParameterizedType parameterizedType, Type srcType, Class<?> declaringClass) {
        Class<?> rawType = (Class<?>) parameterizedType.getRawType();
        Type[] typeArgs = parameterizedType.getActualTypeArguments();
        Type[] args = new Type[typeArgs.length];
        for (int i = 0; i < typeArgs.length; i++) {
            if (typeArgs[i] instanceof TypeVariable) {
                args[i] = resolveTypeVar((TypeVariable<?>) typeArgs[i], srcType, declaringClass);
            } else if (typeArgs[i] instanceof ParameterizedType) {
                args[i] = resolveParameterizedType((ParameterizedType) typeArgs[i], srcType, declaringClass);
            } else if (typeArgs[i] instanceof WildcardType) {
                args[i] = resolveWildcardType((WildcardType) typeArgs[i], srcType, declaringClass);
            } else {
                args[i] = typeArgs[i];
            }
        }
        return new ParameterizedTypeImpl(rawType, null, args);
    }

    private static Type resolveWildcardType(WildcardType wildcardType, Type srcType, Class<?> declaringClass) {
        Type[] lowerBounds = resolveWildcardTypeBounds(wildcardType.getLowerBounds(), srcType, declaringClass);
        Type[] upperBounds = resolveWildcardTypeBounds(wildcardType.getUpperBounds(), srcType, declaringClass);
        return new WildcardTypeImpl(lowerBounds, upperBounds);
    }

    private static Type[] resolveWildcardTypeBounds(Type[] bounds, Type srcType, Class<?> declaringClass) {
        Type[] result = new Type[bounds.length];
        for (int i = 0; i < bounds.length; i++) {
            if (bounds[i] instanceof TypeVariable) {
                result[i] = resolveTypeVar((TypeVariable<?>) bounds[i], srcType, declaringClass);
            } else if (bounds[i] instanceof ParameterizedType) {
                result[i] = resolveParameterizedType((ParameterizedType) bounds[i], srcType, declaringClass);
            } else if (bounds[i] instanceof WildcardType) {
                result[i] = resolveWildcardType((WildcardType) bounds[i], srcType, declaringClass);
            } else {
                result[i] = bounds[i];
            }
        }
        return result;
    }

    private static Type resolveTypeVar(TypeVariable<?> typeVar, Type srcType, Class<?> declaringClass) {
        Type result = null;
        Class<?> clazz = null;
        if (srcType instanceof Class) {
            clazz = (Class<?>) srcType;
        } else if (srcType instanceof ParameterizedType) {
            ParameterizedType parameterizedType = (ParameterizedType) srcType;
            clazz = (Class<?>) parameterizedType.getRawType();
        } else {
            throw new IllegalArgumentException("The 2nd arg must be Class or ParameterizedType, but was: " + srcType.getClass());
        }

        if (clazz == declaringClass) {
            Type[] bounds = typeVar.getBounds();
            if(bounds.length > 0) {
                return bounds[0];
            }
            return Object.class;
        }

        Type superclass = clazz.getGenericSuperclass();
        result = scanSuperTypes(typeVar, srcType, declaringClass, clazz, superclass);
        if (result != null) {
            return result;
        }

        Type[] superInterfaces = clazz.getGenericInterfaces();
        for (Type superInterface : superInterfaces) {
            result = scanSuperTypes(typeVar, srcType, declaringClass, clazz, superInterface);
            if (result != null) {
                return result;
            }
        }
        return Object.class;
    }

    private static Type scanSuperTypes(TypeVariable<?> typeVar, Type srcType, Class<?> declaringClass, Class<?> clazz, Type superclass) {
        if (superclass instanceof ParameterizedType) {
            ParameterizedType parentAsType = (ParameterizedType) superclass;
            Class<?> parentAsClass = (Class<?>) parentAsType.getRawType();
            TypeVariable<?>[] parentTypeVars = parentAsClass.getTypeParameters();
            if (srcType instanceof ParameterizedType) {
                parentAsType = translateParentTypeVars((ParameterizedType) srcType, clazz, parentAsType);
            }
            if (declaringClass == parentAsClass) {
                for (int i = 0; i < parentTypeVars.length; i++) {
                    if (typeVar == parentTypeVars[i]) {
                        return parentAsType.getActualTypeArguments()[i];
                    }
                }
            }
            if (declaringClass.isAssignableFrom(parentAsClass)) {
                return resolveTypeVar(typeVar, parentAsType, declaringClass);
            }
        } else if (superclass instanceof Class && declaringClass.isAssignableFrom((Class<?>) superclass)) {
            return resolveTypeVar(typeVar, superclass, declaringClass);
        }
        return null;
    }

    private static ParameterizedType translateParentTypeVars(ParameterizedType srcType, Class<?> srcClass, ParameterizedType parentType) {
        Type[] parentTypeArgs = parentType.getActualTypeArguments();
        Type[] srcTypeArgs = srcType.getActualTypeArguments();
        TypeVariable<?>[] srcTypeVars = srcClass.getTypeParameters();
        Type[] newParentArgs = new Type[parentTypeArgs.length];
        boolean noChange = true;
        for (int i = 0; i < parentTypeArgs.length; i++) {
            if (parentTypeArgs[i] instanceof TypeVariable) {
                for (int j = 0; j < srcTypeVars.length; j++) {
                    if (srcTypeVars[j] == parentTypeArgs[i]) {
                        noChange = false;
                        newParentArgs[i] = srcTypeArgs[j];
                    }
                }
            } else {
                newParentArgs[i] = parentTypeArgs[i];
            }
        }
        return noChange ? parentType : new ParameterizedTypeImpl((Class<?>)parentType.getRawType(), null, newParentArgs);
    }

    private TypeParameterResolver() {
        super();
    }

    static class ParameterizedTypeImpl implements ParameterizedType {
        private Class<?> rawType;

        private Type ownerType;

        private Type[] actualTypeArguments;

        public ParameterizedTypeImpl(Class<?> rawType, Type ownerType, Type[] actualTypeArguments) {
            super();
            this.rawType = rawType;
            this.ownerType = ownerType;
            this.actualTypeArguments = actualTypeArguments;
        }

        @Override
        public Type[] getActualTypeArguments() {
            return actualTypeArguments;
        }

        @Override
        public Type getOwnerType() {
            return ownerType;
        }

        @Override
        public Type getRawType() {
            return rawType;
        }

        @Override
        public String toString() {
            return "ParameterizedTypeImpl [rawType=" + rawType + ", ownerType=" + ownerType + ", actualTypeArguments=" + Arrays.toString(actualTypeArguments) + "]";
        }
    }

    static class WildcardTypeImpl implements WildcardType {
        private Type[] lowerBounds;

        private Type[] upperBounds;

        WildcardTypeImpl(Type[] lowerBounds, Type[] upperBounds) {
            super();
            this.lowerBounds = lowerBounds;
            this.upperBounds = upperBounds;
        }

        @Override
        public Type[] getLowerBounds() {
            return lowerBounds;
        }

        @Override
        public Type[] getUpperBounds() {
            return upperBounds;
        }
    }

    static class GenericArrayTypeImpl implements GenericArrayType {
        private Type genericComponentType;

        GenericArrayTypeImpl(Type genericComponentType) {
            super();
            this.genericComponentType = genericComponentType;
        }

        @Override
        public Type getGenericComponentType() {
            return genericComponentType;
        }
    }
}

示例参考源码中单元测试类 TypeParameterResolverTest