session共享解决方案

主流的session共享方案:将session统一存储在内存数据库redis或memcached或soler或其他,
面临的问题

　　1. session获取，不是从application的服务器上获取，要从memcached上获取。

　　2. session属性的获取及设置，不是设置到application服务器上，而是操作memcached获取或者设置。

解决问题的方法

　　重写获取session方法:1. 使用一个HttpServletRequestWrapper(HttpServletRequest的装饰类)的实现类，重写getSession()方法，然后使用filter，来过滤每个请求，使request变为requestWrapper。

　　重写设置session键值的方法:2. 使用一个HttpSessionAttributeListener的实现类，重写attributeAdded()、attributeRemoved()、attributeReplaced()方法，当属性发生改变时需要通知memcached中的session发生改变
详细代码:

属性监听器:

import java.io.IOException;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;

import org.springframework.util.StringUtils;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.javacodegeeks.util.JacksonMapUtil;
import com.javacodegeeks.util.MemcachedUtil;

public class MySessionAttributeListener
implements HttpSessionAttributeListener {
private static AtomicInteger count=new AtomicInteger(0);
private static AtomicInteger countU=new AtomicInteger(0);

@Override
public void attributeAdded(HttpSessionBindingEvent event) {
int ss=count.incrementAndGet();
HttpSession session=event.getSession();
//String sessionId=(String) session.getAttribute("JPHPSESSID");
String sessionId="davidwang456";
String attributeName = event.getName();
Object attributeValue = event.getValue();
System.out.println("Attribute add " + attributeName + " : " + attributeValue+",ss="+ss);
String json=MemcachedUtil.getValue(sessionId);
if(StringUtils.isEmpty(json)){
return ;
}
String json_new;
try {
json_new = attributeAddOrUpdate(json,attributeName,attributeValue);
MemcachedUtil.setValue(sessionId, json_new);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

private String attributeAddOrUpdate(String json,String key,Object value)
throws JsonParseException, JsonMappingException, IOException{
ObjectMapper mapper=JacksonMapUtil.getMapper();
@SuppressWarnings("unchecked")
Map<String,Object> userData = mapper.readValue(json, Map.class);
Boolean flag=String.class.isAssignableFrom(value.getClass());
if(!flag){
Map<String, Object> map = mapper.convertValue(value, Map.class);
userData.putAll(map);
}else{
userData.put(key, value);
}
return mapper.writeValueAsString(userData);
}

private String attributeDel(String json, String key)
throws JsonParseException, JsonMappingException, IOException {
ObjectMapper mapper = JacksonMapUtil.getMapper();
@SuppressWarnings("unchecked")
Map<String, Object> userData = mapper.readValue(json, Map.class);
userData.remove(key);
return mapper.writeValueAsString(userData);
}

@Override
public void attributeRemoved(HttpSessionBindingEvent event) {
HttpSession session=event.getSession();
//String sessionId=(String) session.getAttribute("JPHPSESSID");
String sessionId="davidwang456";
String attributeName = event.getName();
System.out.println("Attribute del : " + attributeName);
String json=MemcachedUtil.getValue(sessionId);
if(StringUtils.isEmpty(json)){
return ;
}
String json_new;
try {
json_new = attributeDel(json,attributeName);
MemcachedUtil.setValue(sessionId, json_new);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

@Override
public void attributeReplaced(HttpSessionBindingEvent event) {

int ssu=countU.incrementAndGet();
HttpSession session=event.getSession();
//String sessionId=(String) session.getAttribute("JPHPSESSID");
String sessionId="davidwang456";
String attributeName = event.getName();
Object attributeValue = event.getValue();
System.out.println("Attribute update " + attributeName + " : " + attributeValue+",ss="+ssu);
String json=MemcachedUtil.getValue(sessionId);
if(StringUtils.isEmpty(json)){
return ;
}
String json_new;
try {
json_new = attributeAddOrUpdate(json,attributeName,attributeValue);
MemcachedUtil.setValue(sessionId, json_new);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

}

wrapper类

import java.io.IOException;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpSession;

import org.springframework.util.StringUtils;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.javacodegeeks.util.JacksonMapUtil;
import com.javacodegeeks.util.MemcachedUtil;

public class GetSessionWrapper extends HttpServletRequestWrapper{
private String sessionId=null;
public GetSessionWrapper(HttpServletRequest request) {
super(request);
}
public GetSessionWrapper(HttpServletRequest request,String sessionId) {
super(request);
this.setSessionId(sessionId);
}

@Override
public HttpSession getSession() {
HttpSession httpSession=super.getSession();
//id-->sessionId;
String id="davidwang456";
String json=MemcachedUtil.getValue(id);
if(StringUtils.isEmpty(json)){
return httpSession;
}
httpSession.setAttribute("JPHPSESSID", id);
// 读取JSON数据
Map<String, Object> userData;
try {
userData = JacksonMapUtil.getMapper().readValue(json, Map.class);
for(Map.Entry<String, Object> entry:userData.entrySet()){
httpSession.setAttribute(entry.getKey(), entry.getValue());
}
} catch (JsonParseException e) {
System.out.println("json字符串不能解析成功！");
} catch (JsonMappingException e) {
System.out.println("json字符串不能映射到Map！");
} catch (IOException e) {
System.out.println("io异常！");
}
return httpSession;
}

@Override
public HttpSession getSession(boolean create) {
HttpSession httpSession=super.getSession(create);
return httpSession;
}
public static void main(String[] args) {
String sessionId="davidwang456";
String json=MemcachedUtil.getValue(sessionId);
System.out.println(json);
}
public String getSessionId() {
return sessionId;
}
public void setSessionId(String sessionId) {
this.sessionId = sessionId;
}
}

 
filter类

import java.io.IOException;

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.HttpServletRequest;

import org.springframework.web.util.WebUtils;

public class FetchSession implements javax.servlet.Filter{
private static final String regex=".*(css|html|ico|html|jpg|jpeg|png|gif|js)";
@Override
public void init(FilterConfig filterConfig) throws ServletException {

}

private static String getSessionId(ServletRequest request){
HttpServletRequest httpRequest=(HttpServletRequest)request;
String sessionId="";
Cookie cookie =WebUtils.getCookie(httpRequest, "PHPSESSID");
if(cookie!=null){
return cookie.getValue();
}
cookie =WebUtils.getCookie(httpRequest, "JSESSIONID");
if(cookie!=null){
sessionId= cookie.getValue();
}
return sessionId;
}

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
String sessionId=getSessionId(request);
HttpServletRequest httpRequest=(HttpServletRequest)request;
String requestedUri=httpRequest.getRequestURL().toString();
System.out.println(requestedUri);
if(requestedUri.matches(regex)){
chain.doFilter(request, response);
return;
}
GetSessionWrapper wrapperRequest=new GetSessionWrapper(httpRequest,sessionId);
//HttpSession httpSession=wrapperRequest.getSession();
chain.doFilter(wrapperRequest, response);
}

@Override
public void destroy() {
}
}