在Spring中实现分布式 session管理
本文主要是在Spring中实现分布式session，采用redis对session进行持久化管理，这样当应用部署的时候，不需要在Resin、Tomcat等容器里面进行分布式配置，方便加入新的节点服务器进行集群扩容，session不依赖各节点的服务器，可直接从redis获取。下面是功能的核心代码：
一、首先在web.xml里面配置
加入拦截器：
<!-- 分布式session start --> <filter> <filter-name>distributedSessionFilter</filter-name> <filter-class>DistributedSessionFilter</filter-class> <init-param> <!-- 必填，密钥.2种方式,1对应为bean，格式为bean:key。2字符串,格式如:afffrfgv--> <param-name>key</param-name> <param-value>xxxxxxxx</param-value> </init-param> <init-param> <!-- 必填，redis对应的bean,格式为bean:xx--> <param-name>cacheBean</param-name> <param-value>bean:redisPersistent</param-value>//DistributedBaseInterFace，对应于此接口，进行session的持久化操作 </init-param> <init-param> <!-- 必填， --> <param-name>cookieName</param-name> <param-value>TESTSESSIONID</param-value> </init-param> </filter> <filter-mapping> <filter-name>distributedSessionFilter</filter-name> <url-pattern>*.do</url-pattern> </filter-mapping> <!-- 分布式session end -->
二、拦截器的实现，核心代码如下
主要有以下的几个类：
- DistributedSessionFilter，
- DistributedSessionManager，
- DistributedHttpSessionWrapper，
- DistributedHttpServletRequestWrapper
1、DistributedSessionFilter实现Filter：
import java.io.IOException;import java.util.HashMap;import java.util.Map;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;public class DistributedSessionFilter implements Filter { private static final Logger log = LoggerFactory.getLogger(DistributedSessionFilter.class); private String cookieName; //主要是对session进行管理的操作 private DistributedSessionManager distributedSessionManager; private String key;} 容器启动时候的初始化方法：
@Override public void init(FilterConfig config) throws ServletException { WebApplicationContext wac = WebApplicationContextUtils.getRequiredWebApplicationContext(config .getServletContext()); String key = config.getInitParameter("key"); String cookieName = config.getInitParameter("cookieName"); String cacheBean = config.getInitParameter("cacheBean"); // 获取bean的名称，配置是"bean:" String redisBeanStr = cacheBean.substring(5); DistributedBaseInterFace distributedCache = (DistributedBaseInterFace) wac.getBean(redisBeanStr); // 获取key，有2种配置方式,1对应为bean，格式为bean:key。2字符串 if (key.startsWith("bean:")) { this.key = (String) wac.getBean(key.substring(5)); } else { this.key = key; } this.cookieName = cookieName; this.distributedSessionManager = DistributedSessionManager.getInstance(distributedCache); //异常处理省略。。。 } 进行实际的请求拦截：
@Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws ServletException, IOException { DistributedHttpServletRequestWrapper distReq = null; try { //请求处理 distReq = createDistributedRequest(servletRequest, servletResponse); filterChain.doFilter(distReq, servletResponse); } catch (Throwable e) { //省略。。。 } finally { if (distReq != null) { try { //处理完成request后，处理session（主要是保存session会话） dealSessionAfterRequest(distReq.getSession()); } catch (Throwable e2) { //省略。。。 } } } } //分布式请求 private DistributedHttpServletRequestWrapper createDistributedRequest(ServletRequest servletRequest, ServletResponse servletResponse) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) servletRequest; HttpServletResponse response = (HttpServletResponse) servletResponse; String userSid = CookieUtil.getCookie(cookieName, request); String actualSid = distributedSessionManager.getActualSid(userSid, request, key); if (StringUtil.isBlank(actualSid)) { if (StringUtil.isNotBlank(userSid)) { log.info("userSid[{}]验证不通过", userSid); } // 写cookie String[] userSidArr = distributedSessionManager.createUserSid(request, key); userSid = userSidArr[0]; CookieUtil.setCookie(cookieName, userSid, request, response); actualSid = userSidArr[1]; } actualSid = "sid:" + actualSid; DistributedHttpSessionWrapper distSession = null; try { Map<String, Object> allAttribute = distributedSessionManager.getSession(actualSid, request.getSession() .getMaxInactiveInterval()); distSession = new DistributedHttpSessionWrapper(actualSid, request.getSession(), allAttribute); } catch (Throwable e) { // 出错，删掉缓存数据 log.error(e.getMessage(), e); Map<String, Object> allAttribute = new HashMap<String, Object>(); distSession = new DistributedHttpSessionWrapper(actualSid, request.getSession(), allAttribute); distributedSessionManager.removeSession(distSession); } DistributedHttpServletRequestWrapper requestWrapper = new DistributedHttpServletRequestWrapper(request, distSession); return requestWrapper; } // request处理完时操作session private void dealSessionAfterRequest(DistributedHttpSessionWrapper session) { if (session == null) { return; } if (session.changed) { distributedSessionManager.saveSession(session); } else if (session.invalidated) { distributedSessionManager.removeSession(session); } else { distributedSessionManager.expire(session); } } 2、DistributedSessionManager，主要处理分布式session，核心代码：
class DistributedSessionManager { protected static final Logger log = LoggerFactory.getLogger(DistributedSessionManager.class); private static DistributedSessionManager instance = null; //redis处理session的接口，自己根据情况实现 private DistributedBaseInterFace distributedBaseInterFace; private static byte[] lock = new byte[1]; private DistributedSessionManager(DistributedBaseInterFace distributedBaseInterFace) { this.distributedBaseInterFace = distributedBaseInterFace; } public static DistributedSessionManager getInstance(DistributedBaseInterFace redis) { if (instance == null) { synchronized (lock) { if (instance == null) { instance = new DistributedSessionManager(redis); } } } return instance; } //获取session public Map<String, Object> getSession(String sid,int second) { String json = this.distributedBaseInterFace.get(sid,second); if (StringUtil.isNotBlank(json)) { return JsonUtil.unserializeMap(json); } return new HashMap<String, Object>(1); } //保存session public void saveSession(DistributedHttpSessionWrapper session) { Map<String, Object> map=session.allAttribute; if(MapUtil.isEmpty(map)){ return; } String json = JsonUtil.serializeMap(map); this.distributedBaseInterFace.set(session.getId(), json, session.getMaxInactiveInterval()); } //删除session public void removeSession(DistributedHttpSessionWrapper session) { distributedBaseInterFace.del(session.getId()); } public void expire(DistributedHttpSessionWrapper session) { distributedBaseInterFace.expire(session.getId(), session.getMaxInactiveInterval()); } /** * 创建cookie的sid */ public String[] createUserSid(HttpServletRequest request, String key) { //... } public String getActualSid(String userSid, HttpServletRequest request, String key) { //... }} 3、DistributedHttpSessionWrapper 实现了 HttpSession，进行分布式session包装，核心代码：
public class DistributedHttpSessionWrapper implements HttpSession { private HttpSession orgiSession; private String sid; boolean changed = false; boolean invalidated = false; Map<String, Object> allAttribute; public DistributedHttpSessionWrapper(String sid, HttpSession session, Map<String, Object> allAttribute) { this.orgiSession = session; this.sid = sid; this.allAttribute = allAttribute; } @Override public String getId() { return this.sid; } @Override public void setAttribute(String name, Object value) { changed = true; allAttribute.put(name, value); } @Override public Object getAttribute(String name) { return allAttribute.get(name); } @Override public Enumeration<String> getAttributeNames() { Set<String> set = allAttribute.keySet(); Iterator<String> iterator = set.iterator(); return new MyEnumeration<String>(iterator); } private class MyEnumeration<T> implements Enumeration<T> { Iterator<T> iterator; public MyEnumeration(Iterator<T> iterator) { super(); this.iterator = iterator; } @Override public boolean hasMoreElements() { return iterator.hasNext(); } @Override public T nextElement() { return iterator.next(); } } @Override public void invalidate() { this.invalidated = true; } @Override public void removeAttribute(String name) { changed = true; allAttribute.remove(name); } @Override public long getCreationTime() { return orgiSession.getCreationTime(); } @Override public long getLastAccessedTime() { return orgiSession.getLastAccessedTime(); } @Override public int getMaxInactiveInterval() { return orgiSession.getMaxInactiveInterval(); } @Override public ServletContext getServletContext() { return orgiSession.getServletContext(); } @Override public Object getValue(String arg0) { return orgiSession.getValue(arg0); } @Override public String[] getValueNames() { return orgiSession.getValueNames(); } @Override public boolean isNew() { return orgiSession.isNew(); } @Override public void putValue(String arg0, Object arg1) { orgiSession.putValue(arg0, arg1); } @Override public void removeValue(String arg0) { orgiSession.removeValue(arg0); } @Override public void setMaxInactiveInterval(int arg0) { orgiSession.setMaxInactiveInterval(arg0); } @Override public HttpSessionContext getSessionContext() { return orgiSession.getSessionContext(); } 4、DistributedHttpServletRequestWrapper 实现了 HttpServletRequestWrapper，包装处理过的session和原始request，核心代码：
public class DistributedHttpServletRequestWrapper extends javax.servlet.http.HttpServletRequestWrapper { private HttpServletRequest orgiRequest; private DistributedHttpSessionWrapper session; public DistributedHttpServletRequestWrapper(HttpServletRequest request, DistributedHttpSessionWrapper session) { super(request); if (session == null){ //异常处理。。 } if (request == null){ //异常处理。。 } this.orgiRequest = request; this.session = session; } public DistributedHttpSessionWrapper getSession(boolean create) { orgiRequest.getSession(create); return session; } public DistributedHttpSessionWrapper getSession() { return session; }} 5、另外，定义DistributedBaseInterFace接口，用来处理session入redis进行持久化操作：
public interface DistributedBaseInterFace { /** * 根据key获取缓存数据 * @param key * @param seconds */ public String get(String key,int seconds); /** * 更新缓存数据 * @param key * @param json * @param seconds */ public void set(String key, String json,int seconds); /** * 删除缓存 * @param key */ public void del(String key); /** * 设置过期数据 * @param key * @param seconds */ public void expire(String key,int seconds); 注：本文只是在Spring中采用redis的方式对session进行管理，还有其他诸多的实现方式，比如在容器里面配置等，设计路由算法让session依赖于集群中的各个节点服务器，，，，，，但redis这种方式在实际应用中还是比较广泛的，LZ公司主要就是采用此方式。
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