本文章主要目的是配置session共享，为了巩固基础，捎带介绍了一些基础知识（网上搜索后觉得最全面的特引过来，节省时间），基础扎实的可以自动忽略。
基础篇：
2.如何封装request和session这两个web项目中最常用的对象（以解决乱码为例）
进阶篇：
3.利用memcache实现session共享
在开发过程中，为了缓解访问压力，往往需要配置负载均衡，也就是相同的项目放在多台机子上，保证一台机子挂了，网站仍然可以正常访问，除了需要使用相同的数据源，资料源之外，最大的问题莫过于session的共享了。这里session共享的核心在于改变原来session中的键值对存放在每台机子各自的内存中的情况，而是把session中的内容集中存放在一个nosql数据库中。
3.1封装request对象：
package com.sse.roadshow.session;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import com.sse.roadshow.common.SpyMemcachedManager;
public class HttpServletRequestWrapper extends
javax.servlet.http.HttpServletRequestWrapper {
String sid = "";
private SpyMemcachedManager spyMemcachedManager;
public HttpServletRequestWrapper(String sid, HttpServletRequest request,SpyMemcachedManager spyMemcachedManager) {
super(request);
this.sid = sid;
this.spyMemcachedManager = spyMemcachedManager;
}
public HttpSession getSession(boolean create) {
return new HttpSessionSidWrapper(this.sid, super.getSession(create), this.spyMemcachedManager);
}
public HttpSession getSession() {
return new HttpSessionSidWrapper(this.sid, super.getSession(), this.spyMemcachedManager);
}
}
通过封装传递数据源，并且覆盖getSession方法，自定义的session对象在下一步
3.2封装session对象
package com.sse.roadshow.session;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpSession;
import com.sse.roadshow.common.Constants;
import com.sse.roadshow.common.SpyMemcachedManager;
import com.sse.roadshow.vo.Enumerator;
public
class HttpSessionSidWrapper
extends HttpSessionWrapper {
private String
sid = "";
private
Map map =
new HashMap();
private SpyMemcachedManager
spyMemcachedManager;
@SuppressWarnings("rawtypes")
public HttpSessionSidWrapper(String
sid, HttpSession session, SpyMemcachedManager
spyMemcachedManager) {
super(session);
if (spyMemcachedManager ==
null) {
System.out.println("spyMemcachedManager is null.....");
return;
}
this.spyMemcachedManager =
spyMemcachedManager;
this.sid =
sid;
Map
memSession = null;
memSession = (Map)
this.spyMemcachedManager.get(sid);
//sid没有加入到session中，需要初始化session，替换为自定义session
if (memSession ==
null) {
// System.out.println("memSession is null");
memSession =
new HashMap();
// this.spyMemcachedManager.set(sid, memSession, Constants.SPMEM_EXPTIME);
if (session !=
null) {
Enumeration<String>
names = session.getAttributeNames();
while (names.hasMoreElements()) {
String
key = (String) names.nextElement();
memSession.put(key,
session.getAttribute(key));
}
}
}
this.map =
memSession;
}
public Object getAttribute(String
key) {
if (this.map !=
null && this.map.containsKey(key)) {
return
this.map.get(key);
}
else {
return
null;
}
}
@SuppressWarnings({
"unchecked", "rawtypes" })
public Enumeration getAttributeNames() {
return (new Enumerator(this.map.keySet(),
true));
// return super.getAttributeNames();
}
public
void invalidate() {
// super.invalidate();
this.map.clear();
long
s1= System.currentTimeMillis();
try {
spyMemcachedManager.delete(sid);
System.out.print("removeSession sid is:" +
sid);
}
finally{
System.out.println(System.currentTimeMillis() -s1);
}
}
public
void removeAttribute(String
name) {
// super.removeAttribute(name);
this.map.remove(name);
attributeChange();
// System.out.print("removeAttribute");
// System.out.println("key : " + name);
}
@SuppressWarnings("unchecked")
public
void setAttribute(String
name, Object value) {
// super.setAttribute(name, value);
this.map.put(name,
value);
attributeChange();
// System.out.print("setAttribute-");
// System.out.println("key : " + name + ", value : " + value);
}
private
void attributeChange() {
spyMemcachedManager.set(sid,
this.map, Constants.MYFILTER_COOKIE_EXPTIME);
}
}
这里覆盖session的操作方法，取值使用我们从memcache中查出来的数据
3.3引入我们刚才封装好的request对象：
使用过滤器过滤对应路径的请求，引入自定义request：
3.3.1自定义过滤器：
package com.sse.roadshow.filter;
import java.io.IOException;
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.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.context.support.WebApplicationContextUtils;
import com.sse.roadshow.common.Constants;
import com.sse.roadshow.common.SpyMemcachedManager;
import com.sse.roadshow.common.Util;
import com.sse.roadshow.session.HttpServletRequestWrapper;
public class MemcachedSessionFilter extends HttpServlet implements Filter {
/**
*
*/
private static final long serialVersionUID = 8928219999641126613L;
// private FilterConfig filterConfig;
private String cookieDomain = "";
private String cookiePath = "/";
private SpyMemcachedManager spyMemcachedManager;
public void doFilter(ServletRequest servletRequest,
ServletResponse servletResponse, FilterChain filterChain)
throws IOException, ServletException {
String sessionId = "XmlBeanDefinitionReaderSid";
HttpServletRequest request = (HttpServletRequest) servletRequest;
HttpServletResponse response = (HttpServletResponse) servletResponse;
Cookie cookies[] = request.getCookies();
Cookie sCookie = null;
String sid = "";
if (cookies != null && cookies.length > 0) {
for (int i = 0; i < cookies.length; i++) {
sCookie = cookies[i];
if (sCookie.getName().equals(sessionId)) {
sid = sCookie.getValue();
}
}
}
if (sid == null || sid.length() == 0) {
sid = java.util.UUID.randomUUID().toString();
Cookie mycookies = new Cookie(sessionId, sid);
mycookies.setMaxAge(-1);
mycookies.setPath("/");
mycookies.setHttpOnly(true);
mycookies.setDomain(Constants.DOMAIN);
response.addCookie(mycookies);
}
spyMemcachedManager = getBean(request);
filterChain.doFilter(new HttpServletRequestWrapper(sid, request, spyMemcachedManager),
servletResponse);
}
private SpyMemcachedManager getBean(HttpServletRequest request) {
if(Util.isNull(spyMemcachedManager)) {
spyMemcachedManager = WebApplicationContextUtils.getWebApplicationContext(request.getServletContext()).getBean(SpyMemcachedManager.class);
}
return spyMemcachedManager;
}
public void init(FilterConfig filterConfig) throws ServletException {
// this.filterConfig = filterConfig;
// this.sessionId = filterConfig.getInitParameter("sessionId");
this.cookiePath = filterConfig.getInitParameter("cookiePath");
if (this.cookiePath == null || this.cookiePath.length() == 0) {
this.cookiePath = "/";
}
this.cookieDomain = filterConfig.getInitParameter("cookieDomain");
if (this.cookieDomain == null) {
this.cookieDomain = Constants.DOMAIN;
}
}
public SpyMemcachedManager getSpyMemcachedManager() {
return spyMemcachedManager;
}
public void setSpyMemcachedManager(SpyMemcachedManager spyMemcachedManager) {
this.spyMemcachedManager = spyMemcachedManager;
}
}
3.3.2.在web.xml中配置filter:
<!-- session共享过滤器 -->
<filter>
<filter-name>mySessionFilter</filter-name>
<filter-class>com.sse.roadshow.filter.MemcachedSessionFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>mySessionFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
这样session共享就配置完毕了。