BeanUtils beanjavaBean与Map互转

http://stackoverflow.com/questions/21720128/beanutils-converting-java-util-map-to-nested-bean



Map转换到Bean
BeanOne.java

import java.util.Map;

public class BeanOne {
    private String fieldOne;
    private Map<String,BeanTwo> fieldTwo;
    public Map<String, BeanTwo> getFieldTwo() {
        return fieldTwo;
    }

    public void setFieldTwo(Map<String, BeanTwo> fieldTwo) {
        this.fieldTwo = fieldTwo;
    }

    public String getFieldOne() {
        return this.fieldOne;
    }

    public void setFieldOne(String fieldOne) {
        this.fieldOne = fieldOne;
    }
}

BeanTwo.java

public class BeanTwo {
    private String fieldOne;

    public String getFieldOne() {
        return this.fieldOne;
    }

    public void setFieldOne(String fieldOne) {
        this.fieldOne = fieldOne;
    }
}

Tester.java

import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.beanutils.BeanUtils;

public class Tester {
    public static void main(String[] args) throws IllegalAccessException,
            InvocationTargetException {
        Map beanTwoMap = new HashMap();
        beanTwoMap.put("fieldOne", "fieldOne2222Value");
        Map beanOneMap = new HashMap();
        beanOneMap.put("fieldOne", "fieldOneValue");
        beanOneMap.put("fieldTwo", beanTwoMap);
        BeanOne beanOne = new BeanOne();
        BeanUtils.populate(beanOne, beanOneMap);
        System.out.println(beanOne.getFieldOne());
        System.out.println(beanOne.getFieldTwo().get("fieldOne"));
    }

}

output will be:-

fieldOneValue
fieldOne2222Value




javaBean与Map<String,Object>互转
方法1： 利用java.beans.Introspector和java.beans.PropertyDescriptor实现 javaBean与Map<String,Object>互转
方法2： 利用org.apache.commons.beanutils.BeanUtils工具类，BeanUtils.populate实现Map 转换为javaBean

package javaStudyDemo.bean.reflect.test;

import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import javaStudyDemo.others.PersonBean;

import org.apache.commons.beanutils.BeanUtils;

/**
 * 当把Person类作为BeanUtilTest的内部类时，程序出错<br>
 * java.lang.NoSuchMethodException: Property '**' has no setter method<br>
 * 本质：内部类 和 单独文件中的类的区别 <br>
 * BeanUtils.populate方法的限制：<br>
 * The class must be public, and provide a public constructor that accepts no arguments. <br>
 * This allows tools and applications to dynamically create new instances of your bean, <br>
 * without necessarily knowing what Java class name will be used ahead of time
 */
public class BeanUtilTest {

    public static void main(String[] args) {

        PersonBean person = new PersonBean();
        Map<String, Object> mp = new HashMap<String, Object>();
        mp.put("name", "Mike");
        mp.put("age", 25);
        mp.put("mN", "male");

        // 将map转换为bean
        transMap2Bean2(mp, person);

        System.out.println("--- transMap2Bean Map Info: ");
        for (Map.Entry<String, Object> entry : mp.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }

        System.out.println("--- Bean Info: ");
        System.out.println("name: " + person.getName());
        System.out.println("age: " + person.getAge());
        System.out.println("mN: " + person.getmN());

        // 将javaBean 转换为map
        Map<String, Object> map = transBean2Map(person);

        System.out.println("--- transBean2Map Map Info: ");
        for (Map.Entry<String, Object> entry : map.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }

    }

    // Map --> Bean 2: 利用org.apache.commons.beanutils 工具类实现 Map --> Bean
    public static void transMap2Bean2(Map<String, Object> map, Object obj) {
        if (map == null || obj == null) {
            return;
        }
        try {
            BeanUtils.populate(obj, map);
        } catch (Exception e) {
            System.out.println("transMap2Bean2 Error " + e);
        }
    }

    // Map --> Bean 1: 利用Introspector,PropertyDescriptor实现 Map --> Bean
    public static void transMap2Bean(Map<String, Object> map, Object obj) {

        try {
            BeanInfo beanInfo = Introspector.getBeanInfo(obj.getClass());
            PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();

            for (PropertyDescriptor property : propertyDescriptors) {
                String key = property.getName();

                if (map.containsKey(key)) {
                    Object value = map.get(key);
                    // 得到property对应的setter方法
                    Method setter = property.getWriteMethod();
                    setter.invoke(obj, value);
                }

            }

        } catch (Exception e) {
            System.out.println("transMap2Bean Error " + e);
        }

        return;

    }

    // Bean --> Map 1: 利用Introspector和PropertyDescriptor 将Bean --> Map
    public static Map<String, Object> transBean2Map(Object obj) {

        if(obj == null){
            return null;
        }        
        Map<String, Object> map = new HashMap<String, Object>();
        try {
            BeanInfo beanInfo = Introspector.getBeanInfo(obj.getClass());
            PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
            for (PropertyDescriptor property : propertyDescriptors) {
                String key = property.getName();

                // 过滤class属性
                if (!key.equals("class")) {
                    // 得到property对应的getter方法
                    Method getter = property.getReadMethod();
                    Object value = getter.invoke(obj);

                    map.put(key, value);
                }

            }
        } catch (Exception e) {
            System.out.println("transBean2Map Error " + e);
        }

        return map;

    }
}

public class PersonBean {

    private String  name;
    private Integer age;
    private String  mN;

    /**
     * @return the mN
     */
    public String getmN() {
        return mN;
    }

    /**
     * @param mN the mN to set
     */
    public void setmN(String mN) {
        this.mN = mN;
    }


    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the age
     */
    public Integer getAge() {
        return age;
    }

    /**
     * @param age the age to set
     */
    public void setAge(Integer age) {
        this.age = age;
    }

}

总结：  javaBean与Map<String,Object>互转利用到了java的内省（ Introspector ）和反射（reflect）机制。 其思路为： 通过类 Introspector 来获取某个对象的 BeanInfo 信息，然后通过 BeanInfo 来获取属性的描述器PropertyDescriptor，再利用属性描述器获取某个属性对应的 getter/setter 方法，然后通过反射机制来getter和setter。