JSP 开发之Spring BeanUtils组件使用


            JSP 开发之Spring BeanUtils组件使用

用于演示的javabean





import java.util.Date;



public class People {



  private String name;

  private int age;

  private Date birth;



  public People(String name, int age, Date birth) {

    super();

    this.name = name;

    this.age = age;

    this.birth = birth;

  }



  public People() {

    super();

    // TODO Auto-generated constructor stub

  }



  @Override

  public String toString() {

    return "People [name=" + name + ", age=" + age + ", birth=" + birth + "]";

  }



  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 Date getBirth() {

    return birth;

  }



  public void setBirth(Date birth) {

    this.birth = birth;

  }



}







测试（所有测试只与源javabean属性值有关，与目标javabean属性值无关） 



当源javabean属性均有值时的目标javabean属性复制情况





@Test

public void springBeanUtilsTest(){

  People oldPeople = new People("oldName",100,new Date());

  People newPeople = new People();



  //BeanUtils.copyProperties(Object source,Object target);  

  BeanUtils.copyProperties(oldPeople, newPeople);



  System.out.println(oldPeople);

  System.out.println(newPeople);

}







输出结果如下





People [name=oldName, age=100, birth=Wed Jul 19 18:46:13 CST 2017]

People [name=oldName, age=100, birth=Wed Jul 19 18:46:13 CST 2017]





当源javabean非Date类型的属性值为null时目标javabean属性的复制情况





@Test

public void springBeanUtilsTest(){

  People oldPeople = new People(null,100,new Date());

  People newPeople = new People("newName",20,null);



  //BeanUtils.copyProperties(Object source,Object target);  

  BeanUtils.copyProperties(oldPeople, newPeople);



  System.out.println(oldPeople);

  System.out.println(newPeople);

}







输出结果如下 



注意:目标javabean中的非null属性值被覆盖为null了





People [name=null, age=100, birth=Wed Jul 19 19:04:48 CST 2017]

People [name=null, age=100, birth=Wed Jul 19 19:04:48 CST 2017]





当源javabean中Date类型的属性值为null时目标javabean中属性值的复制情况





@Test

public void springBeanUtilsTest(){

  People oldPeople = new People("oldName",100,null);

  People newPeople = new People("newName",20,new Date());



  //BeanUtils.copyProperties(Object source,Object target);  

  BeanUtils.copyProperties(oldPeople, newPeople);



  System.out.println(oldPeople);

  System.out.println(newPeople);

}







输出结果如下





People [name=oldName, age=100, birth=null]

People [name=oldName, age=100, birth=null]



BeanUtils.copyProperties(Object source,Object target);方法有一个不足的地方，就是当source里的属性对应的属性值为null时，也会覆盖掉target里相同属性名的属性，即使target中该属性值已存在且不为null的属性值，这显然有些不合理，这是我们可以使用它的一个重载方法：





BeanUtils.copyProperties(Object source,Object target, String... ignoreProperties);



最后一个参数的含义是，复制属性值时忽略的属性名称，所有我们只要找出source中属性值为null的属性名称数组即可，方法如下：





/**

 * 

 * @Title: getNullPropertyNames 

 * @Description: 获取一个对象中属性值为null的属性名字符串数组

 * @param source

 * @return

 */

public static String[] getNullPropertyNames (Object source) {

  final BeanWrapper src = new BeanWrapperImpl(source);

  java.beans.PropertyDescriptor[] pds = src.getPropertyDescriptors();



  Set<String> emptyNames = new HashSet<String>();

  for(java.beans.PropertyDescriptor pd : pds) {

    Object srcValue = src.getPropertyValue(pd.getName());

    if (srcValue == null) emptyNames.add(pd.getName());

  }

  String[] result = new String[emptyNames.size()];

  return emptyNames.toArray(result);

}







测试





@Test

public void copyBeanNotNull(){

  People oldPeople = new People(null, 100, null);

  People newPeople = new People("newName", 20, new Date());



  //BeanUtils.copyProperties(Object source,Object target, String... ignoreProperties);  

  BeanUtils.copyProperties(oldPeople, newPeople, getNullPropertyNames(oldPeople));



  System.out.println(oldPeople);

  System.out.println(newPeople);

  for(String key : getNullPropertyNames(oldPeople)){

    System.out.println(key);

  }

}







输出结果如下





People [name=null, age=100, birth=null]

People [name=newName, age=100, birth=Wed Jul 19 23:31:05 CST 2017]

name

birth







以上就是JSP中Spring BeanUtils组件的使用，如有疑问请留言或者到本站社区交流讨论，感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！