JSP 开发之Spring BeanUtils组件使用

2024-09-05 00:18:54

字体：大中小

来源：转载

供稿：网友

JavaBean在程序中的操作非常频繁，但总有一些开源组件易于使用和扩展，为众多开发人员提供了便利，下面一起来了解JSP 开发之Spring BeanUtils组件使用的知识。

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

@Testpublic 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

@Testpublic 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

@Testpublic 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

@Testpublic 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]namebirth我们看完了以上介绍的JSP 开发之Spring BeanUtils组件使用，可以关注错新技术频道小编之后推出的文章哦，希望大家要继续加油。

上一篇：ResourceBundle类在jsp中的国际化实现方法

下一篇：JSP Spring配置文件中传值的实例详解