摘自 ： https://www.cnblogs.com/imyjy/p/9187168.html
背景:
　　Springboot 2.0 (spring-session-data-redis + spring-boot-starter-web)
需求:

通过cookies中取到的 sessionid 获取到 session

预期效果:

@Autowired

private SessionRepositry sessionRepositry;

…

Session session = sessionRespositry.findById(sessionId);

真实结果: 获取到的session是null, 然而通过 request.getSession(); 可以获取到session, 说明 session是存在的.

问题追踪后发现问题:

cookie中的sessionId 与 session.getId() 不一样!!!

DEBUG:
　　1. 先看一看SpringSession是如何从Cookie中获取sessionid的! (相关类: org.springframework.session.web.http.DefaultCookieSerializer)

2. 再看一看 useBase64Encoding 的值是啥, 首先看默认值

3. 看看这些配置是在哪里被(赋值)确认的, 一路追踪到 org.springframework.session.config.annotation.web.http.SpringHttpSessionConfiguration 配置类中

　看看 createDefaultCookieSerializer() 是如何实现的

4. 从上面可以得出结论, 我们无法 通过配置文件 中 server.servlet.session.** 来配置 useBase64Encoding. 使 cookie中的 sessionid 与 session.getId() 保持一致

5. 期间发现的另一个问题: 虽然 sessionCookieConfig 有httpOnly相关配置, 但这里并未将配置设入 cookieSerializer 中, 导致配置文件中的 server.servlet.session.cookie.httpOnly = false 不起作用

解决方案:

第一种方案: 通过配置 自定义的 CookieSerializer 来指定配置信息(如果觉得麻烦请直接看第二种方案), 如下

a) 首先因为 SessionCookieConfig 接口中并没有定义 isUseBase64Encoding() 等接口, 导致缺少了部分配置, 所以我 自定义了一个 MySessionCookieConfig 接口继承了 SessionCookieConfig, 并写了一个默认实现 MyDefaultSessionCookieConfig
　
　　MySessionCookieConfig

package com.cardgame.demo.center.config;

import javax.servlet.SessionCookieConfig;

/**
 *
 * 补充 SessionCookie 中未定义的配置项
 * @author yjy
 * 2018-06-15 13:30
 */
public interface MySessionCookieConfig extends SessionCookieConfig {

    String getDomainPattern();

    void setDomainPattern(String domainPattern);

    String getJvmRoute();

    void setJvmRoute(String jvmRoute);

    boolean isUseBase64Encoding();

    void setUseBase64Encoding(boolean useBase64Encoding);

}

MyDefaultSessionCookieConfig

package com.cardgame.demo.center.config;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

/**
 *
 * 涵盖 CookieSerializer 所有配置项
 * @author yjy
 * 2018-06-15 13:31
 */
@Component
@ConfigurationProperties(prefix = "server.servlet.session.cookie")
public class MyDefaultSessionCookieConfig implements MySessionCookieConfig {

    private String name = "SESSION";
    private String path;
    private String domain;
    private String comment;
    private int maxAge = -1;
    private String domainPattern;
    private String jvmRoute;
    private boolean httpOnly = true;
    private boolean secure = false;
    private boolean useBase64Encoding = false;

    @Override
    public String getDomainPattern() {
        return domainPattern;
    }

    @Override
    public void setDomainPattern(String domainPattern) {
        this.domainPattern = domainPattern;
    }

    @Override
    public String getJvmRoute() {
        return jvmRoute;
    }

    @Override
    public void setJvmRoute(String jvmRoute) {
        this.jvmRoute = jvmRoute;
    }

    @Override
    public boolean isUseBase64Encoding() {
        return useBase64Encoding;
    }

    @Override
    public void setUseBase64Encoding(boolean useBase64Encoding) {
        this.useBase64Encoding = useBase64Encoding;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String getPath() {
        return path;
    }

    @Override
    public void setPath(String path) {
        this.path = path;
    }

    @Override
    public String getDomain() {
        return domain;
    }

    @Override
    public void setDomain(String domain) {
        this.domain = domain;
    }

    @Override
    public String getComment() {
        return comment;
    }

    @Override
    public void setComment(String comment) {
        this.comment = comment;
    }

    @Override
    public boolean isHttpOnly() {
        return httpOnly;
    }

    @Override
    public void setHttpOnly(boolean httpOnly) {
        this.httpOnly = httpOnly;
    }

    @Override
    public boolean isSecure() {
        return secure;
    }

    @Override
    public void setSecure(boolean secure) {
        this.secure = secure;
    }

    @Override
    public int getMaxAge() {
        return maxAge;
    }

    @Override
    public void setMaxAge(int maxAge) {
        this.maxAge = maxAge;
    }
}

b) 利用 MyDefaultSessionCookieConfig 携带的配置, 自定义 CookieSerializer Bean

package com.cardgame.demo.center.config;

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.session.data.redis.config.annotation.web.http.EnableRedisHttpSession;
import org.springframework.session.security.web.authentication.SpringSessionRememberMeServices;
import org.springframework.session.web.http.CookieSerializer;
import org.springframework.session.web.http.DefaultCookieSerializer;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;

import javax.servlet.ServletContext;
import javax.servlet.SessionCookieConfig;

/**
 *
 * @author yjy
 * 2018-06-08 14:53
 */
@Slf4j
@Configuration
@EnableRedisHttpSession(maxInactiveIntervalInSeconds = 3600, redisNamespace = "center")
public class RedisSessionConfig implements ApplicationContextAware {

    @Bean
    public CookieSerializer cookieSerializer(ServletContext servletContext, MySessionCookieConfig sessionCookieConfig) {
        DefaultCookieSerializer cookieSerializer = new DefaultCookieSerializer();
        if (servletContext != null) {
            if (sessionCookieConfig != null) {
                if (sessionCookieConfig.getName() != null)
                    cookieSerializer.setCookieName(sessionCookieConfig.getName());
                if (sessionCookieConfig.getDomain() != null)
                    cookieSerializer.setDomainName(sessionCookieConfig.getDomain());
                if (sessionCookieConfig.getPath() != null)
                    cookieSerializer.setCookiePath(sessionCookieConfig.getPath());
                if (sessionCookieConfig.getMaxAge() != -1)
                    cookieSerializer.setCookieMaxAge(sessionCookieConfig.getMaxAge());
                if (sessionCookieConfig.getDomainPattern() != null)
                    cookieSerializer.setDomainNamePattern(sessionCookieConfig.getDomainPattern());
                if (sessionCookieConfig.getJvmRoute() != null)
                    cookieSerializer.setJvmRoute(sessionCookieConfig.getJvmRoute());
                cookieSerializer.setUseSecureCookie(sessionCookieConfig.isSecure());
                cookieSerializer.setUseBase64Encoding(sessionCookieConfig.isUseBase64Encoding());
                cookieSerializer.setUseHttpOnlyCookie(sessionCookieConfig.isHttpOnly());
            }
        }
        if (ClassUtils.isPresent(
                "org.springframework.security.web.authentication.RememberMeServices",
                null)) {
            boolean usesSpringSessionRememberMeServices = !ObjectUtils
                    .isEmpty(this.context
                            .getBeanNamesForType(SpringSessionRememberMeServices.class));
            if (usesSpringSessionRememberMeServices) {
                cookieSerializer.setRememberMeRequestAttribute(
                        SpringSessionRememberMeServices.REMEMBER_ME_LOGIN_ATTR);
            }
        }
        return cookieSerializer;
    }

    private ApplicationContext context;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.context = applicationContext;
    }
}

c) 修改配置文件配置

d) 配置完成后重新启动, 再看 SpringHttpSessionConfiguration 加载的时候, 拿到了我们自定义的 CookieSerializer, 我想要的配置都有了!! 打开浏览器测试通过!!

第二种方案: 拿到 Cookie 中的 sessionId 后, 手动解码, 再 通过 sessionRespositry.findById(sessionId); 获取session

a) 解码的方案 从 DefaultSerializer 类中 copy 一个 , 如下:

/**
 * Decode the value using Base64.
 * @param base64Value the Base64 String to decode
 * @return the Base64 decoded value
 * @since 1.2.2
 */
private String base64Decode(String base64Value) {
    try {
        byte[] decodedCookieBytes = Base64.getDecoder().decode(base64Value);
        return new String(decodedCookieBytes);
    }
    catch (Exception e) {
        return null;
    }
}

b) 获取步骤:

String cookieSessionId = “XXX”;

String sessionId = base64Decode(cookieSessionId);

Session session = sessionRespositry.findById(sessionId);

c) 搞定! (此方案未解决 httpOnly 不起效的问题, 如果要解决 httpOnly = false , 请看方案一)