JSP 開發之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();
SetString> emptyNames = new HashSetString>();
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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