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

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！