30个类手写Spring核心原理之自定义ORM（下）（7）

本文节选自《Spring 5核心原理》

3 基于Spring JDBC实现关键功能

3.1 ClassMappings

ClassMappings主要定义基础的映射类型，代码如下：

package com.tom.orm.framework;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.math.BigDecimal;
import java.sql.Date;
import java.sql.Timestamp;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class ClassMappings {

   private ClassMappings(){}
   
    static final Set> SUPPORTED_SQL_OBJECTS = new HashSet>();

       static {
          //只要这里写了，默认支持自动类型转换
           Class[] classes = {
                   boolean.class, Boolean.class,
                   short.class, Short.class,
                   int.class, Integer.class,
                   long.class, Long.class,
                   float.class, Float.class,
                   double.class, Double.class,
                   String.class,
                   Date.class,
                   Timestamp.class,
                   BigDecimal.class
           };
           SUPPORTED_SQL_OBJECTS.addAll(Arrays.asList(classes));
       }

       static boolean isSupportedSQLObject(Class clazz) {
           return clazz.isEnum() || SUPPORTED_SQL_OBJECTS.contains(clazz);
       }

       public static Map findPublicGetters(Class clazz) {
           Map map = new HashMap();
           Method[] methods = clazz.getMethods();
           for (Method method : methods) {
               if (Modifier.isStatic(method.getModifiers()))
                   continue;
               if (method.getParameterTypes().length != 0)
                   continue;
               if (method.getName().equals("getClass"))
                   continue;
               Class returnType = method.getReturnType();
               if (void.class.equals(returnType))
                   continue;
               if(!isSupportedSQLObject(returnType)){
                  continue;
               }
               if ((returnType.equals(boolean.class)
                       || returnType.equals(Boolean.class))
                       && method.getName().startsWith("is")
                       && method.getName().length() > 2) {
                   map.put(getGetterName(method), method);
                   continue;
               }
               if ( ! method.getName().startsWith("get"))
                   continue;
               if (method.getName().length() < 4)
                   continue;
               map.put(getGetterName(method), method);
           }
           return map;
       }
       
       public static Field[] findFields(Class clazz){
           return clazz.getDeclaredFields();
       }

       public static Map findPublicSetters(Class clazz) {
           Map map = new HashMap();
           Method[] methods = clazz.getMethods();
           for (Method method : methods) {
               if (Modifier.isStatic(method.getModifiers()))
                   continue;
               if ( ! void.class.equals(method.getReturnType()))
                   continue;
               if (method.getParameterTypes().length != 1)
                   continue;
               if ( ! method.getName().startsWith("set"))
                   continue;
               if (method.getName().length() < 4)
                   continue;
               if(!isSupportedSQLObject(method.getParameterTypes()[0])){
                  continue;
               }
               map.put(getSetterName(method), method);
           }
           return map;
       }

       public static String getGetterName(Method getter) {
           String name = getter.getName();
           if (name.startsWith("is"))
               name = name.substring(2);
           else
               name = name.substring(3);
           return Character.toLowerCase(name.charAt(0)) + name.substring(1);
       }

       private static String getSetterName(Method setter) {
           String name = setter.getName().substring(3);
           return Character.toLowerCase(name.charAt(0)) + name.substring(1);
       }
}

3.2 EntityOperation

EntityOperation主要实现数据库表结构和对象类结构的映射关系，代码如下：

package com.tom.orm.framework;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Transient;
import org.apache.log4j.Logger;
import org.springframework.jdbc.core.RowMapper;
import javax.core.common.utils.StringUtils;

/**
 * 实体对象的反射操作
 *
 * @param 
 */
public class EntityOperation {
   private Logger log = Logger.getLogger(EntityOperation.class);
   public Class entityClass = null; // 泛型实体Class对象
   public final Map mappings;
   public final RowMapper rowMapper;
   
   public final String tableName;
   public String allColumn = "*";
   public Field pkField;
   
   public EntityOperation(Class clazz,String pk) throws Exception{
      if(!clazz.isAnnotationPresent(Entity.class)){
         throw new Exception("在" + clazz.getName() + "中没有找到Entity注解，不能做ORM映射");
      }
      this.entityClass = clazz;
      Table table = entityClass.getAnnotation(Table.class);
       if (table != null) {
             this.tableName = table.name();
       } else {
             this.tableName =  entityClass.getSimpleName();
       }
      Map getters = ClassMappings.findPublicGetters(entityClass);
       Map setters = ClassMappings.findPublicSetters(entityClass);
       Field[] fields = ClassMappings.findFields(entityClass);
       fillPkFieldAndAllColumn(pk,fields);
       this.mappings = getPropertyMappings(getters, setters, fields);
       this.allColumn = this.mappings.keySet().toString().replace("[", "").replace("]",""). replaceAll(" ","");
       this.rowMapper = createRowMapper();
   }
   
    Map getPropertyMappings(Map getters, Map setters, Field[] fields) {
        Map mappings = new HashMap();
        String name;
        for (Field field : fields) {
            if (field.isAnnotationPresent(Transient.class))
                continue;
            name = field.getName();
            if(name.startsWith("is")){
               name = name.substring(2);
            }
            name = Character.toLowerCase(name.charAt(0)) + name.substring(1);
            Method setter = setters.get(name);
            Method getter = getters.get(name);
            if (setter == null || getter == null){
                continue;
            }
            Column column = field.getAnnotation(Column.class);
            if (column == null) {
                mappings.put(field.getName(), new PropertyMapping(getter, setter, field));
            } else {
                mappings.put(column.name(), new PropertyMapping(getter, setter, field));
            }
        }
        return mappings;
    }
    
   RowMapper createRowMapper() {
           return new RowMapper() {
               public T mapRow(ResultSet rs, int rowNum) throws SQLException {
                   try {
                       T t = entityClass.newInstance();
                       ResultSetMetaData meta = rs.getMetaData();
                       int columns = meta.getColumnCount();
                       String columnName;
                       for (int i = 1; i <= columns; i++) {
                           Object value = rs.getObject(i);
                           columnName = meta.getColumnName(i);
                           fillBeanFieldValue(t,columnName,value);
                       }
                       return t;
                   }catch (Exception e) {
                       throw new RuntimeException(e);
                   }
               }
           };
       }

   protected void fillBeanFieldValue(T t, String columnName, Object value) {
       if (value != null) {
             PropertyMapping pm = mappings.get(columnName);
             if (pm != null) {
                 try {
               pm.set(t, value);
            } catch (Exception e) {
               e.printStackTrace();
            }
             }
         }
   }

   private void fillPkFieldAndAllColumn(String pk, Field[] fields) {
      //设定主键
       try {
          if(!StringUtils.isEmpty(pk)){
             pkField = entityClass.getDeclaredField(pk);
             pkField.setAccessible(true);
          }
       } catch (Exception e) {
             log.debug("没找到主键列，主键列名必须与属性名相同");
       }
      for (int i = 0 ; i < fields.length ;i ++) {
         Field f = fields[i];
         if(StringUtils.isEmpty(pk)){
            Id id = f.getAnnotation(Id.class);
            if(id != null){
               pkField = f;
               break;
            }
         }
      }
   }
     
   public T parse(ResultSet rs) {
      T t = null;
      if (null == rs) {
         return null;
      }
      Object value = null;
      try {
         t = (T) entityClass.newInstance();
         for (String columnName : mappings.keySet()) {
            try {
               value = rs.getObject(columnName);
            } catch (Exception e) {
               e.printStackTrace();
            }
            fillBeanFieldValue(t,columnName,value);
         }
      } catch (Exception ex) {
         ex.printStackTrace();
      }
      return t;
   }

   public Map parse(T t) {
      Map _map = new TreeMap();
      try {
         
         for (String columnName : mappings.keySet()) {
            Object value = mappings.get(columnName).getter.invoke(t);
            if (value == null)
               continue;
            _map.put(columnName, value);

         }
      } catch (Exception e) {
         e.printStackTrace();
      }
      return _map;
   }

   public void println(T t) {
      try {
         for (String columnName : mappings.keySet()) {
            Object value = mappings.get(columnName).getter.invoke(t);
            if (value == null)
               continue;
            System.out.println(columnName + " = " + value);
         }
      } catch (Exception e) {
         e.printStackTrace();
      }
   }
}

class PropertyMapping {

    final boolean insertable;
    final boolean updatable;
    final String columnName;
    final boolean id;
    final Method getter;
    final Method setter;
    final Class enumClass;
    final String fieldName;

    public PropertyMapping(Method getter, Method setter, Field field) {
        this.getter = getter;
        this.setter = setter;
        this.enumClass = getter.getReturnType().isEnum() ? getter.getReturnType() : null;
        Column column = field.getAnnotation(Column.class);
        this.insertable = column == null || column.insertable();
        this.updatable = column == null || column.updatable();
        this.columnName = column == null ? ClassMappings.getGetterName(getter) : ("".equals(column.name()) ? ClassMappings.getGetterName(getter) : column.name());
        this.id = field.isAnnotationPresent(Id.class);
        this.fieldName = field.getName();
    }

    @SuppressWarnings("unchecked")
    Object get(Object target) throws Exception {
        Object r = getter.invoke(target);
        return enumClass == null ? r : Enum.valueOf(enumClass, (String) r);
    }

    @SuppressWarnings("unchecked")
    void set(Object target, Object value) throws Exception {
        if (enumClass != null && value != null) {
            value = Enum.valueOf(enumClass, (String) value);
        }
        //BeanUtils.setProperty(target, fieldName, value);
        try {
            if(value != null){
                setter.invoke(target, setter.getParameterTypes()[0].cast(value));
             }
      } catch (Exception e) {
         e.printStackTrace();
         /**
          * 出错原因如果是boolean字段、mysql字段类型，设置tinyint(1)
          */
         System.err.println(fieldName + "--" + value);
      }
      
    }
}

3.3 QueryRuleSqlBuilder

QueryRuleSqlBuilder根据用户构建好的QueryRule来自动生成SQL语句，代码如下：

package com.tom.orm.framework;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.commons.lang.ArrayUtils;
import com.tom.orm.framework.QueryRule.Rule;
import javax.core.common.utils.StringUtils;


/**
 * 根据QueryRule自动构建SQL语句
 */
public class QueryRuleSqlBuilder {

   private int CURR_INDEX = 0; //记录参数所在的位置
   private List properties; //保存列名列表
   private List