Servlet--HttpServletRequest接口，HttpServletResponse接口

标签：

• HttpServletRequest接口

用来处理一个对 Servlet 的 HTTP 格式的请求信息。

• HttpServletResponse 类

使用给定的路径，给客户端发出一个临时转向的响应（SC_MOVED_TEMPORARILY ）。给 定 的 路 径 必 须 是 绝 对 URL 。 相 对 URL 将 不 能 被 接 收 ， 会 抛 出 一 个IllegalArgumentException。这个方法必须在响应被提交之前调用。调用这个方法后，响应立即被提交。在调用这个方法后，Servlet 不会再有更多的输出。

这个方法很有必要说一下，注意了这里接口里面说明的是：一定要是绝对路径。

但是在实际开发中，我们既可以写相对路径，也可以写绝对路径，这是为什么呢？

打开tomcat里面response的源码一看就明白了：

public void sendRedirect(String location) 
        throws IOException {

        if (isCommitted())
            throw new IllegalStateException
                (sm.getString("coyoteResponse.sendRedirect.ise"));

        // Ignore any call from an included servlet
        if (included)
            return; 

        // Clear any data content that has been buffered
        resetBuffer();

        // Generate a temporary redirect to the specified location
        try {
            String absolute = toAbsolute(location);
            setStatus(SC_FOUND);
            setHeader("Location", absolute);
        } catch (IllegalArgumentException e) {
            setStatus(SC_NOT_FOUND);
        }

        // Cause the response to be finished (from the application perspective)
        setSuspended(true);

    }

 /**
     * Convert (if necessary) and return the absolute URL that represents the
     * resource referenced by this possibly relative URL.  If this URL is
     * already absolute, return it unchanged.
     *
     * @param location URL to be (possibly) converted and then returned
     *
     * @exception IllegalArgumentException if a MalformedURLException is
     *  thrown when converting the relative URL to an absolute one
     */
    private String toAbsolute(String location) {

        if (location == null)
            return (location);

        boolean leadingSlash = location.startsWith("/");

        if (leadingSlash || !hasScheme(location)) {

            redirectURLCC.recycle();

            String scheme = request.getScheme();
            String name = request.getServerName();
            int port = request.getServerPort();

            try {
                redirectURLCC.append(scheme, 0, scheme.length());
                redirectURLCC.append("://", 0, 3);
                redirectURLCC.append(name, 0, name.length());
                if ((scheme.equals("http") && port != 80)
                    || (scheme.equals("https") && port != 443)) {
                    redirectURLCC.append(':');
                    String portS = port + "";
                    redirectURLCC.append(portS, 0, portS.length());
                }
                if (!leadingSlash) {
                    String relativePath = request.getDecodedRequestURI();
                    int pos = relativePath.lastIndexOf('/');
                    relativePath = relativePath.substring(0, pos);
                    
                    String encodedURI = null;
                    final String frelativePath = relativePath;
                    if (SecurityUtil.isPackageProtectionEnabled() ){
                        try{
                            encodedURI = (String)AccessController.doPrivileged( 
                                new PrivilegedExceptionAction(){                                
                                    public Object run() throws IOException{
                                        return urlEncoder.encodeURL(frelativePath);
                                    }
                           });   
                        } catch (PrivilegedActionException pae){
                            IllegalArgumentException iae =
                                new IllegalArgumentException(location);
                            iae.initCause(pae.getException());
                            throw iae;
                        }
                    } else {
                        encodedURI = urlEncoder.encodeURL(relativePath);
                    }
                    redirectURLCC.append(encodedURI, 0, encodedURI.length());
                    redirectURLCC.append('/');
                }
                redirectURLCC.append(location, 0, location.length());
            } catch (IOException e) {
                IllegalArgumentException iae =
                    new IllegalArgumentException(location);
                iae.initCause(e);
                throw iae;
            }

            return redirectURLCC.toString();

        } else {

            return (location);

        }

    }

7、setDateHeader

Servlet--HttpServletRequest接口，HttpServletResponse接口

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原文地址：http://blog.csdn.net/u011794238/article/details/46503947