spring session入门

参考资料:
http://projects.spring.io/spring-session/#quick-start
http://docs.spring.io/spring-session/docs/current-SNAPSHOT/reference/html5/guides/httpsession.html#httpsession-sample

spring session提供以下功能:
1.API and implementations for managing a user's session
2.HttpSession - allows replacing the HttpSession in an application container (i.e. Tomcat) neutral way
2.1.Clustered Sessions - Spring Session makes it trivial to support clustered sessions without being tied to an application container specific solution.
2.2.Multiple Browser Sessions - Spring Session supports managing multiple users' sessions in a single browser instance (i.e. multiple authenticated accounts similar to Google).
2.3.RESTful APIs - Spring Session allows providing session ids in headers to work with RESTful APIs
3.WebSocket - provides the ability to keep the HttpSession alive when receiving WebSocket messages

仅是集群session功能,都是振奋人心的.spring session是通过filter嵌入去实现的(spring security也是使用这种方式),下面是个例子.

1.主要依赖

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1. <dependency>  
2.     <groupId>org.slf4j</groupId>  
3.     <artifactId>jcl-over-slf4j</artifactId>  
4.     <version>${slf4j.version}</version>  
5. </dependency>  
6. <dependency>  
7.     <groupId>org.slf4j</groupId>  
8.     <artifactId>slf4j-log4j12</artifactId>  
9.     <version>${slf4j.version}</version>  
10. </dependency>  
11. <dependency>  
12.     <groupId>org.springframework</groupId>  
13.     <artifactId>spring-webmvc</artifactId>  
14.     <version>${spring.version}</version>  
15.     <exclusions>  
16.         <exclusion>  
17.             <groupId>commons-logging</groupId>  
18.             <artifactId>commons-logging</artifactId>  
19.         </exclusion>  
20.     </exclusions>  
21. </dependency>  
22. <dependency>  
23.     <groupId>org.springframework</groupId>  
24.     <artifactId>spring-tx</artifactId>  
25.     <version>${spring.version}</version>  
26. </dependency>  
27. <dependency>  
28.     <groupId>org.springframework</groupId>  
29.     <artifactId>spring-aop</artifactId>  
30.     <version>${spring.version}</version>  
31. </dependency>  
32. <dependency>  
33.     <groupId>org.springframework</groupId>  
34.     <artifactId>spring-context-support</artifactId>  
35.     <version>${spring.version}</version>  
36. </dependency>  
37. <dependency>  
38.     <groupId>org.springframework.data</groupId>  
39.     <artifactId>spring-data-redis</artifactId>  
40.     <version>1.4.1.RELEASE</version>  
41. </dependency>  
42. <dependency>  
43.     <groupId>redis.clients</groupId>  
44.     <artifactId>jedis</artifactId>  
45.     <version>2.5.2</version>  
46. </dependency>  
47. <dependency>  
48.     <groupId>org.springframework.session</groupId>  
49.     <artifactId>spring-session</artifactId>  
50.     <version>${spring.session.version}</version>  
51. </dependency>  

2.写一个configuration来启用RedisHttpSession,在这个配置注册一个redis客户端的连接工厂Bean,供Spring Session用于与redis服务端交互.

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1. package org.exam.config;  
2. import org.springframework.context.annotation.Bean;  
3. import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;  
4. import org.springframework.session.data.redis.config.annotation.web.http.EnableRedisHttpSession;  
5. /** 
6.  * Created by xin on 15/1/20. 
7.  */  
8. @EnableRedisHttpSession  
9. public class SessionConfig {  
10.     @Bean  
11.     public JedisConnectionFactory connectionFactory() {  
12.         return new JedisConnectionFactory();  
13.     }  
14. }  

3.写一个Initializer,主要用于向应用容器添加springSessionRepositoryFilter.

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1. package org.exam.config;  
2. import org.springframework.session.web.context.AbstractHttpSessionApplicationInitializer;  
3. /** 
4.  * Created by xin on 15/1/20. 
5.  */  
6. public class SessionApplicationInitializer extends AbstractHttpSessionApplicationInitializer {  
7. }  

4.将SessionConfig加入到org.exam.config.DispatcherServletInitializer#getRootConfigClasses

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1. @Override  
2. protected Class<?>[] getRootConfigClasses() {  
3.     return new Class<?>[] {AppConfig.class,SessionConfig.class};  
4. }  

5.使用例子.

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1. package org.exam.web;  
2. import org.springframework.stereotype.Controller;  
3. import org.springframework.ui.Model;  
4. import org.springframework.web.bind.annotation.RequestMapping;  
5. import javax.servlet.http.HttpServletRequest;  
6. import javax.servlet.http.HttpSession;  
7. /** 
8.  * Created by xin on 15/1/7. 
9.  */  
10. @Controller  
11. public class DefaultController {  
12.     @RequestMapping("/")  
13.     public String index(Model model,HttpServletRequest request,String action,String msg){  
14.         HttpSession session=request.getSession();  
15.         if ("set".equals(action)){  
16.             session.setAttribute("msg", msg);  
17.         }else if ("get".equals(action)){  
18.             String message=(String)session.getAttribute("msg");  
19.             model.addAttribute("msgFromRedis",message);  
20.         }  
21.         return "index";  
22.     }  
23. }  

得到这个被spring session包装过的session,像平常一样直接使用.
6.测试.先启动redis服务端.
请求:localhost:8080/testweb/?action=set&msg=123   把123通过spring session set到redis去.
请求:localhost:8080/testweb/?action=get  从redis取出刚才存入的值.

从redis删除存入去相关的值,再次请求localhost:8080/testweb/?action=get查看结果

下面顺便跟踪下实现吧:

1.注册springSessionRepositoryFilter位置在:org.springframework.session.web.context.AbstractHttpSessionApplicationInitializer#insertSessionRepositoryFilter,从org.springframework.web.filter.DelegatingFilterProxy#initDelegate可以看出会去找名为springSessionRepositoryFilter Bean的实现作为Filter的具体实现.
2.因为使用了@EnableRedisHttpSession,就会使用org.springframework.session.data.redis.config.annotation.web.http.RedisHttpSessionConfiguration,这个配置里注册的springSessionRepositoryFilter Bean就是SessionRepositoryFilter.即springSessionRepositoryFilter的实现为org.springframework.session.web.http.SessionRepositoryFilter
3.Filter每一次的请求都会调用doFilter,即调用SessionRepositoryFilter的父类OncePerRequestFilter的doFilter,此方法会调用SessionRepositoryFilter自身的doFilterInternal.这个方法如下:

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1. protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {  
2.     request.setAttribute(SESSION_REPOSITORY_ATTR, sessionRepository);  
3.     SessionRepositoryRequestWrapper wrappedRequest = new SessionRepositoryRequestWrapper(request, response);  
4.     SessionRepositoryResponseWrapper wrappedResponse = new SessionRepositoryResponseWrapper(wrappedRequest,response);  
5.     HttpServletRequest strategyRequest = httpSessionStrategy.wrapRequest(wrappedRequest, wrappedResponse);  
6.     HttpServletResponse strategyResponse = httpSessionStrategy.wrapResponse(wrappedRequest, wrappedResponse);  
7.     try {  
8.         filterChain.doFilter(strategyRequest, strategyResponse);  
9.     } finally {  
10.         wrappedRequest.commitSession();  
11.     }  
12. }  

4.从这里就知request经过了包装,当然里面的getSession方法也重写了.org.springframework.session.web.http.SessionRepositoryFilter.SessionRepositoryRequestWrapper#getSession(boolean)方法如下:

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1. public HttpSession getSession(boolean create) {  
2.     if(currentSession != null) {  
3.         return currentSession;  
4.     }  
5.     String requestedSessionId = getRequestedSessionId();  
6.     if(requestedSessionId != null) {  
7.     S session = sessionRepository.getSession(requestedSessionId);  
8.         if(session != null) {  
9.             this.requestedValidSession = true;  
10.             currentSession = new HttpSessionWrapper(session, getServletContext());  
11.             currentSession.setNew(false);  
12.             return currentSession;  
13.         }  
14.     }  
15.     if(!create) {  
16.         return null;  
17.     }  
18.     S session = sessionRepository.createSession();  
19.     currentSession = new HttpSessionWrapper(session, getServletContext());  
20.     return currentSession;  
21. }  

即上面的例子调用getSession会调用此方法来获取Session.而此Session是通过sessionRepository创建的,此处注入的是org.springframework.session.data.redis.RedisOperationsSessionRepository(sessionRepository的注册也是在org.springframework.session.data.redis.config.annotation.web.http.RedisHttpSessionConfiguration),而不是应用服务器本身去创建的.