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！