request对象的setAttribute()方法究竟有什么用呢？

我做tag解析时深入了解过这个问题,在JAVA中,通过WEB服务器传递数据方式分两种,一种是session,一种是request,使用方法如下:
1.使用request传:
request.setAttribute("beanobject", sample); //其中sample为bean

2.使用session传:
HttpSession s = request.getSession();
s.setAttribute("beanobject", sample); //其中sample为bean

传递时,数据还原成object并且放在request或session中传递,到达目的地后再还原成原来的类型,struts在这方面做得比较好,他在BeanUtil中提供了相应的还原接口,在写时,struts解析时会把setAttribute的bean以object形式拿出,然后取里面property的值,我做解析时使用自己的方法,如下:

************************ Main.java ************************
package reflect;
import java.io.*;
public class Main {
 public static void main(String[] args) throws IOException{
  
  Bean1 bean1 = new Bean1();
  
  System.out.println( Reflect.get(bean1, "getName", 0) );
  System.out.println( Reflect.get(bean1, "getOld", 0) );
  
  System.out.println( Reflect.get(bean1, "getName", 1) );
  System.out.println( Reflect.get(bean1, "getOld", 1) );
  
  System.out.println( Reflect.get(bean1, "getName", 2) );
  System.out.println( Reflect.get(bean1, "getOld", 2) );
  
  System.out.println( Reflect.get(bean1, "getName", 3) );
  System.out.println( Reflect.get(bean1, "getOld", 3) );
  
  System.out.println( Reflect.get(bean1, "getName", 4) );
  System.out.println( Reflect.get(bean1, "getOld", 4) );
  
  Bean2 bean2 = new Bean2();
  
  System.out.println( Reflect.get(bean2, "getMember", 0) );
  System.out.println( Reflect.get(bean2, "getYear", 0) );
  
  System.out.println( Reflect.get(bean2, "getMember", 1) );
  System.out.println( Reflect.get(bean2, "getYear", 1) );
  
  System.out.println( Reflect.get(bean2, "getMember", 2) );
  System.out.println( Reflect.get(bean2, "getYear", 2) );
  
  System.out.println( Reflect.get(bean2, "getMember", 3) );
  System.out.println( Reflect.get(bean2, "getYear", 3) );
  
  System.out.println( Reflect.get(bean2, "getMember", 4) );
  System.out.println( Reflect.get(bean2, "getYear", 4) );
  
 }
}

************************ Reflect.java ************************
package reflect;

import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.util.ArrayList;

public class Reflect {
 
 public static String get(Object object, String methodname, int i){
  
  Class cls = object.getClass();
  
  Object ret;

  try {

   Method method = cls.getMethod(methodname, null);
   
   ret = method.invoke(cls.newInstance(), null);
   
   ArrayList array = new ArrayList();

   if (ret.getClass().isArray()) {
   
    ret = Array.get(ret, i);
   
   }
   
  } catch (Exception e) {
   
   ret = null;
   
  }
  
  if(ret == null){
   return null;
  }
  
  return ret.toString();
 }
}

************************ Bean1.java ************************
package reflect;

public class Bean1 {
 String[] name = {"赵","钱","孙","李"};
 int[] old = {28, 27, 32, 26};
 
 public String[] getName(){
  return name;
 }
 
 public int[] getOld(){
  return old;
 }
}

************************ Bean2.java ************************
package reflect;

public class Bean2 {
 String[] member = {"张","刘","王","方"};
 int[] year = {31, 28, 30, 36};
 
 public String[] getMember(){
  return member;
 }
 
 public int[] getYear(){
  return year;
 }
}

大家注意:主要是Reflect.java,你只要将bean的名字和getproperty的名字给他,他就能把数据传回给你.