BeanUtils.copyProperties()的用法
BeanUtils提供对Java反射和自省API的包装。其主要目的是利用反射机制对JavaBean的属性进行处理。我们知道，一个JavaBean通常包含了大量的属性，很多情况下，对JavaBean的处理导致大量get/set代码堆积，增加了代码长度和阅读代码的难度。下面通过代码来理解BeanUtils
首先创建两个类
Person.java
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[*]package com.org;
[*]
[*]import java.util.Date;
[*]
[*]public class Person {
[*] private String name;
[*] private String sex;
[*] private int age;
[*] private Date birthday;
[*]
[*] public String getName() {
[*] return name;
[*] }
[*]
[*] public void setName(String name) {
[*] this.name = name;
[*] }
[*]
[*] public String getSex() {
[*] return sex;
[*] }
[*]
[*] public void setSex(String sex) {
[*] this.sex = sex;
[*] }
[*]
[*] public int getAge() {
[*] return age;
[*] }
[*]
[*] public void setAge(int age) {
[*] this.age = age;
[*] }
[*]
[*] public Date getBirthday() {
[*] return birthday;
[*] }
[*]
[*] public void setBirthday(Date birthday) {
[*] this.birthday = birthday;
[*] }
[*]
[*]
[*]}
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[*]package com.org;
[*]
[*]import java.util.Date;
[*]
[*]public class Person {
[*] private String name;
[*] private String sex;
[*] private int age;
[*] private Date birthday;
[*]
[*] public String getName() {
[*] return name;
[*] }
[*]
[*] public void setName(String name) {
[*] this.name = name;
[*] }
[*]
[*] public String getSex() {
[*] return sex;
[*] }
[*]
[*] public void setSex(String sex) {
[*] this.sex = sex;
[*] }
[*]
[*] public int getAge() {
[*] return age;
[*] }
[*]
[*] public void setAge(int age) {
[*] this.age = age;
[*] }
[*]
[*] public Date getBirthday() {
[*] return birthday;
[*] }
[*]
[*] public void setBirthday(Date birthday) {
[*] this.birthday = birthday;
[*] }
[*]
[*]
[*]}
Student.java view plaincopy
[*]package com.org;
[*]
[*]import java.util.Date;
[*]
[*]public class Student {
[*] private String name;
[*] private int age;
[*] private String address;
[*] private Date birthday;
[*]
[*] 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 getAddress() {
[*] return address;
[*] }
[*] public void setAddress(String address) {
[*] this.address = address;
[*] }
[*] public Date getBirthday() {
[*] return birthday;
[*] }
[*] public void setBirthday(Date birthday) {
[*] this.birthday = birthday;
[*] }
[*]
[*]
[*]}
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[*]package com.org;
[*]
[*]import java.util.Date;
[*]
[*]public class Student {
[*] private String name;
[*] private int age;
[*] private String address;
[*] private Date birthday;
[*]
[*] 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 getAddress() {
[*] return address;
[*] }
[*] public void setAddress(String address) {
[*] this.address = address;
[*] }
[*] public Date getBirthday() {
[*] return birthday;
[*] }
[*] public void setBirthday(Date birthday) {
[*] this.birthday = birthday;
[*] }
[*]
[*]
[*]}
测试类BeanUtilTest.java view plaincopy
[*]package com.org;
[*]
[*]import java.lang.reflect.InvocationTargetException;
[*]import java.util.Date;
[*]
[*]//import com.sun.org.apache.commons.beanutils.BeanUtils;
[*]
[*]import org.apache.commons.beanutils.BeanUtils;
[*]
[*]public class BeanUtilTest {
[*] public static void main(String[] args) {
[*] Person per = new Person();
[*] Student stu = new Student();
[*]
[*] per.setName("zhangsan");
[*] per.setSex("男");
[*] per.setAge(20);
[*] per.setBirthday(new Date());
[*]
[*] stu.setName("wuangwu");
[*] stu.setAddress("北京市");
[*] try {
[*] BeanUtils.copyProperties(stu, per);
[*]
[*] } catch (IllegalAccessException e) {
[*] // TODO Auto-generated catch block
[*] e.printStackTrace();
[*] } catch (InvocationTargetException e) {
[*] // TODO Auto-generated catch block
[*] e.printStackTrace();
[*] }
[*] System.out.println(stu.getName());
[*] System.out.println(stu.getAge());
[*] System.out.println(stu.getAddress());
[*] System.out.println(stu.getBirthday());
[*]
[*] }
[*]}
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[*]package com.org;
[*]
[*]import java.lang.reflect.InvocationTargetException;
[*]import java.util.Date;
[*]
[*]//import com.sun.org.apache.commons.beanutils.BeanUtils;
[*]
[*]import org.apache.commons.beanutils.BeanUtils;
[*]
[*]public class BeanUtilTest {
[*] public static void main(String[] args) {
[*] Person per = new Person();
[*] Student stu = new Student();
[*]
[*] per.setName("zhangsan");
[*] per.setSex("男");
[*] per.setAge(20);
[*] per.setBirthday(new Date());
[*]
[*] stu.setName("wuangwu");
[*] stu.setAddress("北京市");
[*] try {
[*] BeanUtils.copyProperties(stu, per);
[*]
[*] } catch (IllegalAccessException e) {
[*] // TODO Auto-generated catch block
[*] e.printStackTrace();
[*] } catch (InvocationTargetException e) {
[*] // TODO Auto-generated catch block
[*] e.printStackTrace();
[*] }
[*] System.out.println(stu.getName());
[*] System.out.println(stu.getAge());
[*] System.out.println(stu.getAddress());
[*] System.out.println(stu.getBirthday());
[*]
[*] }
[*]}
程序输出结果为： view plaincopy
[*]zhangsan
[*]20
[*]北京市
[*]Fri Nov 25 13:03:29 CST 2011
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[*]zhangsan
[*]20
[*]北京市
[*]Fri Nov 25 13:03:29 CST 2011
可见Student自己设置的值都被Person给覆盖了 再做下面两个测试
把Person中的setName和setAge 改为setnamesetage程序输出结果为
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[*]zhangsan
[*]20
[*]北京市
[*]Fri Nov 25 13:08:34 CST 2011
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[*]zhangsan
[*]20
[*]北京市
[*]Fri Nov 25 13:08:34 CST 2011
结果没有改变 而如果改为setNAme, setAGe结果为：
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[*]wuangwu
[*]0
[*]北京市
[*]Fri Nov 25 13:10:25 CST 2011
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[*]wuangwu
[*]0
[*]北京市
[*]Fri Nov 25 13:10:25 CST 2011
我们发现结果改变了内容没有被覆盖
注： 当我们加载BeanUtils类时 可能会报如下错误
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[*]Exception in thread "main" java.lang.ExceptionInInitializerError
[*] at com.org.BeanUtilTest.main(BeanUtilTest.java:101)
[*]Caused by: com.sun.org.apache.commons.logging.LogConfigurationException: com.sun.org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException) (Caused by com.sun.org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException))
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543)
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235)
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209)
[*] at com.sun.org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351)
[*] at com.sun.org.apache.commons.beanutils.BeanUtils.<clinit>(BeanUtils.java:111)
[*] ... 1 more
[*]Caused by: com.sun.org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException)
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:397)
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529)
[*] ... 5 more
[*]Caused by: java.lang.NullPointerException
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:374)
[*] ... 6 more
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[*]Exception in thread "main" java.lang.ExceptionInInitializerError
[*] at com.org.BeanUtilTest.main(BeanUtilTest.java:101)
[*]Caused by: com.sun.org.apache.commons.logging.LogConfigurationException: com.sun.org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException) (Caused by com.sun.org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException))
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543)
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235)
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209)
[*] at com.sun.org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351)
[*] at com.sun.org.apache.commons.beanutils.BeanUtils.<clinit>(BeanUtils.java:111)
[*] ... 1 more
[*]Caused by: com.sun.org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException)
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:397)
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529)
[*] ... 5 more
[*]Caused by: java.lang.NullPointerException
[*] at com.sun.org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:374)
[*] ... 6 more
产生错误的原因是引入的包不对，应引入import org.apache.commons.beanutils.BeanUtils; 而不应是import com.sun.org.apache.commons.beanutils.BeanUtils;
另外所需jar包为：
commons-beanutils-1.8.3.jar
commons-logging-1.1.1.jar
还有一个很邪门的问题 实在令我不解
就是如果把Person，Student 测试类写在一起的话会产生问题
类似与这样的结构
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[*]class Person{
[*] .....
[*]}
[*]class Student{
[*] .....
[*]}
[*]
[*]public class BeanUtilTest {
[*] public static void main(String[] args) {
[*] ......
[*] }
[*]}
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