BeanUtils 工具类

一.BeanUtils 概述
     BeanUtils 是阿帕奇提供的一套专门用于将一些数据封装到java对象中的工具类;
    
     名词:javaBean:特定格式的java类称为javaBean;
    
     要求:
         1:javaBean这个类要实现Serializable接口;(在实际开发中,通常省略了)
         2:javaBean必须有public权限的空参数的构造方法;
         3:javaBean必须有属性对应的getXxx与setter方法;

二.BeanUtils 的使用
     Beanutils 有2个依赖jar包;commons-beanutils-1.8.3.jar和commons-logging-1.1.1.jar;
     BeanUtils 有2个核心类:BeanUtils,ConvertUtils 类;
     使用步骤:
         1:下载解压;
         2:复制核心jar包到工程中;(有2个)
         3:添加到本地;(add to build path)
         4:使用核心类;

三.BeanUtils 常用方法
     public static void setProperty(Object bean,String name,Object value)
                             throws IllegalAccessException,InvocationTargetException{}:向bean对象的name属性中保存value值;
     public static String getProperty(Object bean,String name)
                               throws IllegalAccessException,InvocationTargetException,NoSuchMethodException{}:从bean对象中获取name属性的值;
     public static String[] getArrayProperty(Object bean,String name)
                                      throws IllegalAccessException,InvocationTargetException,NoSuchMethodException{}:从bean对象中获取name属性的数组类型的值;
     [注:getProperty方法就只认String类型和String[]数组类型,其它类型它会自动帮你转成这两个类型,使用时需时刻想到String类型,用""包裹属性]
     public static void populate(Object bean,Map properties)
                                     throws IllegalAccessException,InvocationTargetException{}:将properties集合中的数据,根据key与bean的属性名(实际上是匹配setXxx方法)    匹配,匹配成功,则赋值,匹配失败不操作;                                                   
代码演示1:(以下代码全在Eclipse中实现)

//创建beanUtilsDemo01包
package beanUtilsDemo01;

import java.util.Arrays;

public class Person {
     // 属性
    private String name;
     private int age;
     private String[] hobby;

    // 构造方法
    public Person() {
        super();
     }

    public Person(String name, int age, String[] hobby) {
         super();
         this.name = name;
         this.age = age;
         this.hobby = hobby;
     }

    // getter/setter
     public String getName() {
         return name;
     }

    public void setName(String name) {
         this.name = name;
     }

    public int getAge() {
         return age;
     }

    public void setAge(int age) {
         this.age = age;
     }

    public String[] getHobby() {
         return hobby;
     }

    public void setHobby(String[] hobby) {
         this.hobby = hobby;
     }

    // 覆写toString/equal/hashcode
     @Override
     public String toString() {
         return "Person [name=" + name + ", age=" + age + ", hobby="
                 + Arrays.toString(hobby) + "]";
     }

    @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
         result = prime * result + age;
         result = prime * result + Arrays.hashCode(hobby);
         result = prime * result + ((name == null) ? 0 : name.hashCode());
         return result;
     }

    @Override
     public boolean equals(Object obj) {
         if (this == obj) {
             return true;
         }
         if (obj == null) {
             return false;
         }
         if (!(obj instanceof Person)) {
             return false;
         }
         Person other = (Person) obj;
         if (age != other.age) {
             return false;
         }
         if (!Arrays.equals(hobby, other.hobby)) {
             return false;
         }
         if (name == null) {
             if (other.name != null) {
                 return false;
             }
         } else if (!name.equals(other.name)) {
             return false;
         }
         return true;
     }

}
 //创建beanUtilsDemo01包
package beanUtilsDemo01;

import java.util.Arrays;

import org.apache.commons.beanutils.BeanUtils;

//BeanUtils常用方法练习

public class Demo01BeanUtils {

    public static void main(String[] args) throws Exception {
         // 实例化对象
        Person p = new Person();
         // 借用BeanUtils工具类向Person对象赋值
        BeanUtils.setProperty(p, "name", "Rose");
         BeanUtils.setProperty(p, "age", 22);
         BeanUtils.setProperty(p, "hobby", new String[] { "eating", "sleeping",
                 "kissing" });
         // 打印对象
        System.out.println(p);
         // 获取各属性值
        String[] hobby = BeanUtils.getArrayProperty(p, "hobby");
         System.out.println(Arrays.toString(hobby));
         String name = BeanUtils.getProperty(p, "name");
         System.out.println(name);
         String age = BeanUtils.getProperty(p, "age");
         System.out.println(age);
     }

}

代码演示2:封装map集合中的数据

package beanUtilsDemo01;

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

import org.apache.commons.beanutils.BeanUtils;

//借用BeanUtils将Map中的数据封装到javabean中

public class Demo02BeanUtils {

    public static void main(String[] args) throws IllegalAccessException,
             InvocationTargetException {
         // 实例化对象
        Person p = new Person();
         // 准备MAP集合
        Map<String, Object> map = new HashMap<>();
         // 向map中添加数据
        map.put("name", "jack");
         map.put("age", 23);
         map.put("hobbyy", new String[] { "eating", "sleeping", "painting" });
         // 将map集合中的数据封装到javabean中
        BeanUtils.populate(p, map);
         System.out.println(p);
     }
 }

代码演示3:与以上利用同一个Person类????????????????????????

package beanUtilsDemo01;

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

import org.apache.commons.beanutils.BeanUtils;

//利用BeanUtils工具类自定义工具类:要求传入任一类型的字节码文件 和 属性的map集合,返回实例化对象
class MyBeanUtils {
     public static <T> T popu(Class<T> c, Map map) throws Exception {    //泛型
        Object obj = c.newInstance();
         BeanUtils.populate(obj, map);
         return (T) obj; //向下转型
    }
 }

public class MyTest {
     public static void main(String[] args) throws Exception {
        Map<String, Object> map = new HashMap<>();
         map.put("name", "rose");
         map.put("age", "18");
         Person p = MyBeanUtils.popu(Person.class, map);
         System.out.println(p);
     }

}

代码演示4:需准备一个User类,和以上的Person类,及data.xml文件

package beanutilcase;

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

import org.apache.commons.beanutils.BeanUtils;
 import org.dom4j.Document;
 import org.dom4j.Element;
 import org.dom4j.io.SAXReader;

public class Demo {

    public static void main(String[] args) throws Exception {
         Person p = new Person();
         User u = new User();
         // 创建解析器对象
        SAXReader sax = new SAXReader();
         // 读取文档,并获取根节点
        Document doc = sax.read("data.xml");
         Element root = doc.getRootElement();
         // 获取根节点下的一级子元素
        List<Element> listFirst = root.elements();
         // 迭代
        for (Element e : listFirst) {
             // 获取一级子元素的属性值
            String path = e.attributeValue("className");
             // 根据路径(属性)获取字节码文件
            Class c = Class.forName(path);
             // 获取二级子元素
            List<Element> listSecond = e.elements();
             // 定义map集合装属性值
            Map<String, Object> map = new HashMap<>();
             for (Element es : listSecond) {
                 // 获取二级子元素的两个属性值
                String name = es.attributeValue("name");
                 String value = es.attributeValue("value");
                 map.put(name, value);
             }
             // 利用beanutils工具类进行封装
            // 判断是否为person
             if (path.matches(".*Person$")) {
                 BeanUtils.populate(p, map);
             } else {
                 BeanUtils.populate(u, map);
             }
         }
         System.out.println(p);
         System.out.println(u);
     }

}