用nginx做负载的时候，会出现每一次http请求都会分配到不同的tomcat上，这样用session存储用户数据就会有问题。因为tomcat集群之间没有实现session共享。

spring-session跟redis很好的帮我们解决了这个问题。

一、引入maven依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>com.cicoding.druid</groupId>
	<artifactId>springboot_session_redis_colony</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>

	<name>springboot_session_redis_colony</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.9.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.session</groupId>
            <artifactId>spring-session-data-redis</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>
</project>

二、配置application.properties

server.port=8082
spring.redis.host=localhost
spring.redis.port=6379
spring.redis.password=redis password

# spring session使用存储类型
spring.session.store-type=redis

• spirngboot默认就是使用redis方式，如果不想用可以填none。

三、在启动类中加入@EnableRedisHttpSession  注解

package com.cicoding;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.session.data.redis.config.annotation.web.http.EnableRedisHttpSession;

@EnableCaching
@EnableRedisHttpSession  
@SpringBootApplication
public class SessionApplication {

	public static void main(String[] args) {
		SpringApplication.run(SessionApplication.class, args);
	}
}

四、编写控制器

package com.cicoding.controller;

import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller
@RequestMapping(value = "/")
public class UserController {

	@ResponseBody
    @RequestMapping(value = "/session")
    public Map<String, Object> getSession(HttpServletRequest request) {
        request.getSession().setAttribute("username", "admin");
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("sessionId", request.getSession().getId());
        return map;
    }

    @ResponseBody
    @RequestMapping(value = "/get")
    public String get(HttpServletRequest request) {
        String userName = (String) request.getSession().getAttribute("username");

        return userName;
    }

}

五、测试

• 先输入http://localhost:8082/session，在session中设置一个值

• 复制这个工程，application.properties中的server.port=8081，然后访问“http://localhost:8081/get”，如下获取到了另一个工程中设置的session的值。

这样两个应用就能拿到同一个session集群共享了session！