Spring MVC session处理---@SessionAttributes

转载自:BazingaLyncc的博客 http://blog.csdn.net/linuu/article/details/51037943

介绍

在web开发中，session的重要性不言而喻，与cookie相比，session更加安全，处于服务器端，开发者经常把一些重要的信息放在session，方便在多次请求中方便的获取信息，Spring MVC 对session的支持也依旧很强大很灵活

Spring MVC对session的支持分为两种

基于HttpSession的天然支持

基于注解@SessionAttributes的灵活多变的支持

首先我们先一起分析一下基于天生的HttpSession的支持吧

假如用户登录的时候，我们把用户信息记录到session中

import javax.servlet.http.HttpSession;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
import org.study.lyncc.web.entity.User;

@Controller
public class SessionAttributesController {

/**
* user对象存入session
* @param id
* @param name
* @param session
* @return
*/
@RequestMapping("/session/test/{id}/{name}")
public ModelAndView localsessionAttributes(@PathVariable Integer id,@PathVariable String name,HttpSession session){
session.setAttribute("currentUser", new User(id,name));
ModelAndView mav = new ModelAndView("session");
return mav;
}

/**
* 获取session中的user对象
* @param session
* @return
*/
@RequestMapping("/session/attributes")
public ModelAndView sessionAttributesage(HttpSession session){
User u = (User)session.getAttribute("currentUser");
System.out.println(u.getUsername());
ModelAndView mav = new ModelAndView("session");
return mav;
}

}

我们先请求 http://localhost:8080/spring-mvc/session/test/1/lyncc

然后我们再次请求 http://localhost:8080/spring-mvc/session/attributes

会发现我们可以冲session取出我们上次请求存入session的user对象，并成功打印user的名字



基于@SessionAttributes注解实现的对session的管理

SessionAttributes是只能注解于类或者接口，@SessionAttributes的value代表我们需要把什么样的对象放入session，在我们的方法后当我们把对象放入ModelMap这个对象的时候，如果给出的key也会自动放入session的，我们举例说明

import javax.servlet.http.HttpSession;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.servlet.ModelAndView;
import org.study.lyncc.web.entity.User;

@Controller
@SessionAttributes(value="currentUser")
public class SessionAttributesController {

@RequestMapping("/session/attributes/{id}/{name}")
public ModelAndView sessionAttributes(@PathVariable Integer id,@PathVariable String name){
ModelAndView mav = new ModelAndView("session");
mav.addObject("currentUser", new User(id,name));
return mav;
}

/**
* 获取session中的user对象
* @param session
* @return
*/
@RequestMapping("/session/attributes")
public ModelAndView sessionAttributesage(HttpSession session){
User u = (User)session.getAttribute("currentUser");
System.out.println(u.getUsername());
ModelAndView mav = new ModelAndView("session");
return mav;
}

}

上面代码中，我们注解了@SessionAttributes，并且在sessionAttributes方法中，mav.addObject(“currentUser”, new User(id,name));我们创建一个对象放入ModelAndView中，因为@SessionAttributes的value与addObject的key值相同，所以该User会自动存入session中（上面说是ModelMap对象，其实看源码就知道ModelAndView的model就是ModelMap）



好了，我们测试一下，先运行http://localhost:8080/spring-mvc/session/test/1/lyncc

再运行http://localhost:8080/spring-mvc/session/attributes，测试结果



能获取到值，说明user放入session成功了

我们除了显性的从HttpSession中获取对象，我们还可以利用@ModelAttribute与@SessionAttributes相互配合，隐性的获取到放在session中的值，代码如下

import javax.servlet.http.HttpSession;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.servlet.ModelAndView;
import org.study.lyncc.web.entity.User;

@Controller
@SessionAttributes(value="currentUser")
public class SessionAttributesController {

@RequestMapping("/session/attributes/{id}/{name}")
public ModelAndView sessionAttributes(@PathVariable Integer id,@PathVariable String name){
ModelAndView mav = new ModelAndView("session");
mav.addObject("currentUser", new User(id,name));
return mav;
}

@RequestMapping("/session/attributes/test")
public ModelAndView sessionAttributesage(@ModelAttribute("currentUser") User u){
System.out.println(u.getUsername());
ModelAndView mav = new ModelAndView("session");
return mav;
}

}

这样依旧能获取到值，不过要注意



最后我们再看看@SessionAttributes这个注解

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.core.annotation.AliasFor;

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface SessionAttributes {

@AliasFor("names")
String[] value() default {};

@AliasFor("value")
String[] names() default {};

Class<?>[] types() default {};

}

都是数组型的，也就说可以支持多个对象放入session中,举例说明

import java.util.Date;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.servlet.ModelAndView;
import org.study.lyncc.web.entity.User;

@Controller
@SessionAttributes(value={"currentUser","saveTime"},types={User.class,Date.class})
public class SessionAttributesController {

@RequestMapping("/session/attributes/{id}/{name}")
public ModelAndView sessionAttributes(@PathVariable Integer id,@PathVariable String name){
ModelAndView mav = new ModelAndView("session");
mav.addObject("currentUser", new User(id,name));
mav.addObject("saveTime", new Date());
return mav;
}

@RequestMapping("/session/attributes/test")
public ModelAndView sessionAttributesage(@ModelAttribute("currentUser") User u,@ModelAttribute("saveTime") Date d){
System.out.println(u.getUsername());
System.out.println(d);
ModelAndView mav = new ModelAndView("session");
return mav;
}
}

测试结果：