BeanUtils.copyProperties()的用法

inushome · 发表于 2015-10-14 09:17:23

　　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
[java] view plaincopy

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;
}
}

[java] view plaincopy

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[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;
}
}

[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;
}
}

测试类 BeanUtilTest.java[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());
}
}

[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());
}
}

程序输出结果为：[plain] view plaincopy

zhangsan
20
北京市
Fri Nov 25 13:03:29 CST 2011

[plain] view plaincopy

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setname setage程序输出结果为
[plain] view plaincopy

zhangsan
20
北京市
Fri Nov 25 13:08:34 CST 2011

[plain] view plaincopy

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：
[plain] view plaincopy

wuangwu
0
北京市
Fri Nov 25 13:10:25 CST 2011

[plain] view plaincopy

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
[java] view plaincopy

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

[java] view plaincopy

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
[java] view plaincopy

class Person{
.....
}
class Student{
.....
}
public class BeanUtilTest {
public static void main(String[] args) {
......
}
}

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