简单的session共享的封装

发布时间：2020-12-14 06:21:19 所属栏目：Java 来源：网络整理

导读：目的 session存储在缓存服务器上(各种缓存服务器上均可，本文以memcached为例)，但对开发者来说，他不用关注，只需要调用request.getSession()方法即可获取到session，然后对session的属性进行操作。面临的问题 1. session获取，不是从application的服务器

目的

　　session存储在缓存服务器上(各种缓存服务器上均可，本文以memcached为例)，但对开发者来说，他不用关注，只需要调用request.getSession()方法即可获取到session，然后对session的属性进行操作。

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

　　1. 使用一个HttpServletRequestWrapper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。

　　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

另外：为解决各个异构系统因语言不通可能发生的兼容问题，session以json字符串存储。

具体代码如下：

wrapper类

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

import org.springframework.util.StringUtils;

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
</span><span style="color: #0000ff;"&gt;public</span><span style="color: #000000;"&gt; HttpSession getSession() {
    HttpSession httpSession</span>=<span style="color: #0000ff;"&gt;super</span><span style="color: #000000;"&gt;.getSession();
    </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt;id-->sessionId;</span>
    String id="davidwang456"<span style="color: #000000;"&gt;;
    String json</span>=<span style="color: #000000;"&gt;MemcachedUtil.getValue(id);
    </span><span style="color: #0000ff;"&gt;if</span><span style="color: #000000;"&gt;(StringUtils.isEmpty(json)){
        </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; httpSession;
    }
    httpSession.setAttribute(</span>"JPHPSESSID"<span style="color: #000000;"&gt;,id);
    </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt; 读取JSON数据</span>
    Map<String,Object><span style="color: #000000;"&gt; userData;
    </span><span style="color: #0000ff;"&gt;try</span><span style="color: #000000;"&gt; {
        userData </span>= JacksonMapUtil.getMapper().readValue(json,Map.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;);
        </span><span style="color: #0000ff;"&gt;for</span>(Map.Entry<String,Object><span style="color: #000000;"&gt; entry:userData.entrySet()){ 
            httpSession.setAttribute(entry.getKey(),entry.getValue());    
       } 
    } </span><span style="color: #0000ff;"&gt;catch</span><span style="color: #000000;"&gt; (JsonParseException e) {
        System.out.println(</span>"json字符串不能解析成功！"<span style="color: #000000;"&gt;);
    } </span><span style="color: #0000ff;"&gt;catch</span><span style="color: #000000;"&gt; (JsonMappingException e) {
        System.out.println(</span>"json字符串不能映射到Map！"<span style="color: #000000;"&gt;);
    } </span><span style="color: #0000ff;"&gt;catch</span><span style="color: #000000;"&gt; (IOException e) {
        System.out.println(</span>"io异常！"<span style="color: #000000;"&gt;);
    }
    </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; httpSession;
}

@Override
</span><span style="color: #0000ff;"&gt;public</span> HttpSession getSession(<span style="color: #0000ff;"&gt;boolean</span><span style="color: #000000;"&gt; create) {
    HttpSession httpSession</span>=<span style="color: #0000ff;"&gt;super</span><span style="color: #000000;"&gt;.getSession(create);
    </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; httpSession;        
}
</span><span style="color: #0000ff;"&gt;public</span> <span style="color: #0000ff;"&gt;static</span> <span style="color: #0000ff;"&gt;void</span><span style="color: #000000;"&gt; main(String[] args) {
    String sessionId</span>="davidwang456"<span style="color: #000000;"&gt;;
    String json</span>=<span style="color: #000000;"&gt;MemcachedUtil.getValue(sessionId);
    System.out.println(json);
}
</span><span style="color: #0000ff;"&gt;public</span><span style="color: #000000;"&gt; String getSessionId() {
    </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; sessionId;
}
</span><span style="color: #0000ff;"&gt;public</span> <span style="color: #0000ff;"&gt;void</span><span style="color: #000000;"&gt; setSessionId(String sessionId) {
    </span><span style="color: #0000ff;"&gt;this</span>.sessionId =<span style="color: #000000;"&gt; sessionId;
}

}

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 {

}

</span><span style="color: #0000ff;"&gt;private</span> <span style="color: #0000ff;"&gt;static</span><span style="color: #000000;"&gt; String getSessionId(ServletRequest request){
    HttpServletRequest httpRequest</span>=<span style="color: #000000;"&gt;(HttpServletRequest)request;
    String sessionId</span>=""<span style="color: #000000;"&gt;;
    Cookie cookie </span>=WebUtils.getCookie(httpRequest,"PHPSESSID"<span style="color: #000000;"&gt;);
    </span><span style="color: #0000ff;"&gt;if</span>(cookie!=<span style="color: #0000ff;"&gt;null</span><span style="color: #000000;"&gt;){
        </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; cookie.getValue();
    }
    cookie </span>=WebUtils.getCookie(httpRequest,"JSESSIONID"<span style="color: #000000;"&gt;);
    </span><span style="color: #0000ff;"&gt;if</span>(cookie!=<span style="color: #0000ff;"&gt;null</span><span style="color: #000000;"&gt;){
        sessionId</span>=<span style="color: #000000;"&gt; cookie.getValue();
    }
    </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; sessionId;
}

@Override
</span><span style="color: #0000ff;"&gt;public</span> <span style="color: #0000ff;"&gt;void</span><span style="color: #000000;"&gt; doFilter(ServletRequest request,ServletResponse response,FilterChain chain) </span><span style="color: #0000ff;"&gt;throws</span><span style="color: #000000;"&gt; IOException,ServletException {
        String sessionId</span>=<span style="color: #000000;"&gt;getSessionId(request);
        HttpServletRequest httpRequest</span>=<span style="color: #000000;"&gt;(HttpServletRequest)request;    
        String requestedUri</span>=<span style="color: #000000;"&gt;httpRequest.getRequestURL().toString();
        System.out.println(requestedUri);
        </span><span style="color: #0000ff;"&gt;if</span><span style="color: #000000;"&gt;(requestedUri.matches(regex)){
            chain.doFilter(request,response);
            </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt;;
        }
        GetSessionWrapper wrapperRequest</span>=<span style="color: #0000ff;"&gt;new</span><span style="color: #000000;"&gt; GetSessionWrapper(httpRequest,sessionId);
        </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt;HttpSession httpSession=wrapperRequest.getSession();</span>

chain.doFilter(wrapperRequest,response);
}

@Override
</span><span style="color: #0000ff;"&gt;public</span> <span style="color: #0000ff;"&gt;void</span><span style="color: #000000;"&gt; destroy() {
}

}

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
</span><span style="color: #0000ff;"&gt;public</span> <span style="color: #0000ff;"&gt;void</span><span style="color: #000000;"&gt; attributeAdded(HttpSessionBindingEvent event) {
    </span><span style="color: #0000ff;"&gt;int</span> ss=<span style="color: #000000;"&gt;count.incrementAndGet();
    HttpSession session</span>=<span style="color: #000000;"&gt;event.getSession();
    </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt;String sessionId=(String) session.getAttribute("JPHPSESSID");</span>
    String sessionId="davidwang456"<span style="color: #000000;"&gt;;
    String attributeName </span>=<span style="color: #000000;"&gt; event.getName();
    Object attributeValue </span>=<span style="color: #000000;"&gt; event.getValue();
    System.out.println(</span>"Attribute add " + attributeName + " : " + attributeValue+",ss="+<span style="color: #000000;"&gt;ss);
    String json</span>=<span style="color: #000000;"&gt;MemcachedUtil.getValue(sessionId);
    </span><span style="color: #0000ff;"&gt;if</span><span style="color: #000000;"&gt;(StringUtils.isEmpty(json)){
        </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; ;
    }
    String json_new;
    </span><span style="color: #0000ff;"&gt;try</span><span style="color: #000000;"&gt; {
        json_new </span>=<span style="color: #000000;"&gt; attributeAddOrUpdate(json,attributeName,attributeValue);
        MemcachedUtil.setValue(sessionId,json_new);
    } </span><span style="color: #0000ff;"&gt;catch</span><span style="color: #000000;"&gt; (Exception e) {
        </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt; TODO Auto-generated catch block</span>

e.printStackTrace();
}
}

</span><span style="color: #0000ff;"&gt;private</span><span style="color: #000000;"&gt; String attributeAddOrUpdate(String json,String key,Object value) 
                        </span><span style="color: #0000ff;"&gt;throws</span><span style="color: #000000;"&gt; JsonParseException,JsonMappingException,IOException{
    ObjectMapper mapper</span>=<span style="color: #000000;"&gt;JacksonMapUtil.getMapper();
    @SuppressWarnings(</span>"unchecked"<span style="color: #000000;"&gt;)
    Map</span><String,Object> userData = mapper.readValue(json,Map.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;);
    Boolean flag</span>=String.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;.isAssignableFrom(value.getClass());
    </span><span style="color: #0000ff;"&gt;if</span>(!<span style="color: #000000;"&gt;flag){
        Map</span><String,Object> map = mapper.convertValue(value,Map.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;);
        userData.putAll(map);
    }</span><span style="color: #0000ff;"&gt;else</span><span style="color: #000000;"&gt;{
        userData.put(key,value);
    }      
    </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; mapper.writeValueAsString(userData); 
}

</span><span style="color: #0000ff;"&gt;private</span><span style="color: #000000;"&gt; String attributeDel(String json,String key)
        </span><span style="color: #0000ff;"&gt;throws</span><span style="color: #000000;"&gt; JsonParseException,IOException {
    ObjectMapper mapper </span>=<span style="color: #000000;"&gt; JacksonMapUtil.getMapper();
    @SuppressWarnings(</span>"unchecked"<span style="color: #000000;"&gt;)
    Map</span><String,Map.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;);
    userData.remove(key);
    </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; mapper.writeValueAsString(userData);
}

@Override
</span><span style="color: #0000ff;"&gt;public</span> <span style="color: #0000ff;"&gt;void</span><span style="color: #000000;"&gt; attributeRemoved(HttpSessionBindingEvent event) {
    HttpSession session</span>=<span style="color: #000000;"&gt;event.getSession();
    </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt;String sessionId=(String) session.getAttribute("JPHPSESSID");</span>
    String sessionId="davidwang456"<span style="color: #000000;"&gt;;
    String attributeName </span>=<span style="color: #000000;"&gt; event.getName();
    System.out.println(</span>"Attribute del : " +<span style="color: #000000;"&gt; attributeName);
    String json</span>=<span style="color: #000000;"&gt;MemcachedUtil.getValue(sessionId);
    </span><span style="color: #0000ff;"&gt;if</span><span style="color: #000000;"&gt;(StringUtils.isEmpty(json)){
        </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; ;
    }
    String json_new;
    </span><span style="color: #0000ff;"&gt;try</span><span style="color: #000000;"&gt; {
        json_new </span>=<span style="color: #000000;"&gt; attributeDel(json,attributeName);
        MemcachedUtil.setValue(sessionId,json_new);
    } </span><span style="color: #0000ff;"&gt;catch</span><span style="color: #000000;"&gt; (Exception e) {
        </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt; TODO Auto-generated catch block</span>

e.printStackTrace();
}
}

@Override
</span><span style="color: #0000ff;"&gt;public</span> <span style="color: #0000ff;"&gt;void</span><span style="color: #000000;"&gt; attributeReplaced(HttpSessionBindingEvent event) {

    </span><span style="color: #0000ff;"&gt;int</span> ssu=<span style="color: #000000;"&gt;countU.incrementAndGet();
    HttpSession session</span>=<span style="color: #000000;"&gt;event.getSession();
    </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt;String sessionId=(String) session.getAttribute("JPHPSESSID");</span>
    String sessionId="davidwang456"<span style="color: #000000;"&gt;;
    String attributeName </span>=<span style="color: #000000;"&gt; event.getName();
    Object attributeValue </span>=<span style="color: #000000;"&gt; event.getValue();
    System.out.println(</span>"Attribute update " + attributeName + " : " + attributeValue+",ss="+<span style="color: #000000;"&gt;ssu);
    String json</span>=<span style="color: #000000;"&gt;MemcachedUtil.getValue(sessionId);
    </span><span style="color: #0000ff;"&gt;if</span><span style="color: #000000;"&gt;(StringUtils.isEmpty(json)){
        </span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; ;
    }
    String json_new;
    </span><span style="color: #0000ff;"&gt;try</span><span style="color: #000000;"&gt; {
        json_new </span>=<span style="color: #000000;"&gt; attributeAddOrUpdate(json,json_new);
    } </span><span style="color: #0000ff;"&gt;catch</span><span style="color: #000000;"&gt; (Exception e) {
        </span><span style="color: #008000;"&gt;//</span><span style="color: #008000;"&gt; TODO Auto-generated catch block</span>

e.printStackTrace();
}

}

com.fasterxml.jackson.core jackson-databind 2.4.3 com.fasterxml.jackson.core jackson-annotations 2.4.3 com.fasterxml.jackson.datatype jackson-datatype-guava 2.4.3 com.fasterxml.jackson.datatype jackson-datatype-joda 2.4.3 com.fasterxml.jackson.datatype jackson-datatype-jsr310 2.4.3 net.spy spymemcached 2.12.0

注意：上面代码仅为demo代码，实际应用需重构代码。

（编辑：李大同）

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