RequestContextHolder

RequestContextHolder顾名思义,持有上下文的Request容器.

SpringMVC 获取request和response

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//两个方法在没有使用JSF的项目中是没有区别的
RequestAttributes requestAttributes = RequestContextHolder.currentRequestAttributes();
//                                            RequestContextHolder.getRequestAttributes();
//从session里面获取对应的值
String str = (String) requestAttributes.getAttribute("name",RequestAttributes.SCOPE_SESSION);

HttpServletRequest request = ((ServletRequestAttributes)requestAttributes).getRequest();
HttpServletResponse response = ((ServletRequestAttributes)requestAttributes).getResponse();

转自：通过RequestContextHolder直接获取HttpServletRequest对象

一次请求，Web应用服务器就会分配一个线程去处理。也就是说，在Service方法中获取到的HttpServletRequest对象需要满足：线程内共享，线程间隔离。
这恰恰是ThreadLocal的应用场景。

###利用ServletRequestListener实现 

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import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpServletRequest;

public class RequestHolder implements ServletRequestListener {

    private static ThreadLocal<HttpServletRequest> httpServletRequestHolder = 
            new ThreadLocal<HttpServletRequest>();
    
    @Override
    public void requestInitialized(ServletRequestEvent requestEvent) {
        HttpServletRequest request = (HttpServletRequest) requestEvent.getServletRequest();
        httpServletRequestHolder.set(request); // 绑定到当前线程
    }
    
    @Override
    public void requestDestroyed(ServletRequestEvent requestEvent) {
        httpServletRequestHolder.remove(); // 清理资源引用
    }
    
    public static HttpServletRequest getHttpServletRequest() {
        return httpServletRequestHolder.get();
    }
    
}

利用Filter实现

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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.HttpServletRequest;

public class RequestHolder implements Filter {

    private static ThreadLocal<HttpServletRequest> httpServletRequestHolder = 
            new ThreadLocal<HttpServletRequest>();

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        httpServletRequestHolder.set((HttpServletRequest) request); // 绑定到当前线程
        try {
            chain.doFilter(request, response);
        } catch (Exception e) {
            throw e;
        } finally {
            httpServletRequestHolder.remove(); // 清理资源引用
        }
    }

    @Override
    public void destroy() {
    }

    public static HttpServletRequest getHttpServletRequest() {
        return httpServletRequestHolder.get();
    }
    
}

利用SpringMVC拦截器实现

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import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

public class RequestHolder extends HandlerInterceptorAdapter {

    private static ThreadLocal<HttpServletRequest> httpServletRequestHolder = 
            new ThreadLocal<HttpServletRequest>();
    
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) 
        throws Exception {
        httpServletRequestHolder.set(request); // 绑定到当前线程
        return true;
    }
    
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, 
            Object handler, Exception ex) 
        throws Exception {
        httpServletRequestHolder.remove(); // 清理资源引用
    }
    
    public static HttpServletRequest getHttpServletRequest() {
        return httpServletRequestHolder.get();
    }
    
}