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JSP 開發(fā)之Spring BeanUtils組件使用

 更新時間：2017年08月04日 09:54:07   投稿：lqh  
這篇文章主要介紹了JSP 開發(fā)之Spring BeanUtils組件使用的相關資料,這里提供實例幫助大家理解如何使用Spring BeanUtils組件,需要的朋友可以參考下

JSP 開發(fā)之Spring BeanUtils組件使用

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;
  }

}

測試（所有測試只與源javabean屬性值有關，與目標javabean屬性值無關）

當源javabean屬性均有值時的目標javabean屬性復制情況

@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);
}

輸出結果如下

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]

當源javabean非Date類型的屬性值為null時目標javabean屬性的復制情況

@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);
}

輸出結果如下

注意:目標javabean中的非null屬性值被覆蓋為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]

當源javabean中Date類型的屬性值為null時目標javabean中屬性值的復制情況

@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);
}

輸出結果如下

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

BeanUtils.copyProperties(Object source,Object target);方法有一個不足的地方，就是當source里的屬性對應的屬性值為null時，也會覆蓋掉target里相同屬性名的屬性，即使target中該屬性值已存在且不為null的屬性值，這顯然有些不合理，這是我們可以使用它的一個重載方法：

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

最后一個參數的含義是，復制屬性值時忽略的屬性名稱，所有我們只要找出source中屬性值為null的屬性名稱數組即可，方法如下：

/**
 * 
 * @Title: getNullPropertyNames 
 * @Description: 獲取一個對象中屬性值為null的屬性名字符串數組
 * @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);
}

測試

@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);
  }
}

輸出結果如下

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組件的使用，如有疑問請留言或者到本站社區(qū)交流討論，感謝閱讀，希望能幫助到大家，謝謝大家對本站的支持！

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