java web 请求和响应 HttpServletResponse（五）

目标：

掌握HttpServletRequest对象的使用，HttpServletResponse对象的使用

熟悉请求转发和请求重定向

了解中文乱码问题的解决

目录

一、HttpServletResponse对象

1.1 发送状态码相关的方法

（1）setStatus(int status)方法:用于设置HTTP响应消息的状态码，并生成响应状态行

（2）sendError(int sc)方法：发送表示错误信息的状态码

1.2发送响应消息头相关的方法

 1.1.1  getOutputStream()方法

1.1.2  getWriter()方法

二、HttpServletResponse应用

 2.1 中文输出乱码问题

​

 2.2 网页定时刷新并跳转

2.4  禁止浏览器缓存页面

 2.5 请求重定向

三、HttpServletRequest对象

3.1获取请求行信息的相关方法

3.2  获取请求消息头的相关方法

 3.3 利用Referer请求头防止“盗链”

3.4  获取请求消息体的相关方法

四、HttpServletRequest应用

4.1  获取请求参数

4.2  获取网络连接信息

4.3 通过request对象传递数据

五、RequestDispatcher对象的应用

5.1 RequestDispatcher接口

5.2请求转发

5.3请求包含

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一、HttpServletResponse对象

1.1 发送状态码相关的方法

在Servlet API中，定义了一个HttpServletResponse接口，它继承自ServletResponse，专门用来封装HTTP响应消息。

在HttpServletResponse接口中，定义了两个发送状态码的方法：

（1）setStatus(int status)方法

（2）sendError(int sc)方法

（1）setStatus(int status)方法:用于设置HTTP响应消息的状态码，并生成响应状态行

      由于响应状态行中的状态描述信息直接与状态码相关，而HTTP版本由服务器确定，因此，只要通过setStatus(int status)方法设置了状态码，即可实现状态行的发送。

注意：需要注意的是，正常情况下，Web服务器会默认产生一个状态码为200的状态行。

（2）sendError(int sc)方法：发送表示错误信息的状态码

 在response对象中，提供了两个重载的sendError(int sc)方法，具体如下：

 

 第一个方法除了发送状态码外，还可以增加一条用于提示说明的文本信息，该文本信息将出现在发送给客户端的正文内容中。而第二个方法只是发送错误信息的状态码。

由于响应状态码是一个三位的十进制数，非常难以记忆，为此，在HttpServletResponse接口中，定义了一系列响应状态码常量。

 /**
     * Status code (100) indicating the client can continue.
     */
    public static final int SC_CONTINUE = 100;

    /**
     * Status code (101) indicating the server is switching protocols according
     * to Upgrade header.
     */
    public static final int SC_SWITCHING_PROTOCOLS = 101;

    /**
     * Status code (200) indicating the request succeeded normally.
     */
    public static final int SC_OK = 200;

    /**
     * Status code (201) indicating the request succeeded and created a new
     * resource on the server.
     */
    public static final int SC_CREATED = 201;

    /**
     * Status code (202) indicating that a request was accepted for processing,
     * but was not completed.
     */
    public static final int SC_ACCEPTED = 202;

    /**
     * Status code (203) indicating that the meta information presented by the
     * client did not originate from the server.
     */
    public static final int SC_NON_AUTHORITATIVE_INFORMATION = 203;

    /**
     * Status code (204) indicating that the request succeeded but that there
     * was no new information to return.
     */
    public static final int SC_NO_CONTENT = 204;

    /**
     * Status code (205) indicating that the agent <em>SHOULD</em> reset the
     * document view which caused the request to be sent.
     */
    public static final int SC_RESET_CONTENT = 205;

    /**
     * Status code (206) indicating that the server has fulfilled the partial
     * GET request for the resource.
     */
    public static final int SC_PARTIAL_CONTENT = 206;

    /**
     * Status code (300) indicating that the requested resource corresponds to
     * any one of a set of representations, each with its own specific location.
     */
    public static final int SC_MULTIPLE_CHOICES = 300;

    /**
     * Status code (301) indicating that the resource has permanently moved to a
     * new location, and that future references should use a new URI with their
     * requests.
     */
    public static final int SC_MOVED_PERMANENTLY = 301;

    /**
     * Status code (302) indicating that the resource has temporarily moved to
     * another location, but that future references should still use the
     * original URI to access the resource. This definition is being retained
     * for backwards compatibility. SC_FOUND is now the preferred definition.
     */
    public static final int SC_MOVED_TEMPORARILY = 302;

    /**
     * Status code (302) indicating that the resource reside temporarily under a
     * different URI. Since the redirection might be altered on occasion, the
     * client should continue to use the Request-URI for future
     * requests.(HTTP/1.1) To represent the status code (302), it is recommended
     * to use this variable.
     */
    public static final int SC_FOUND = 302;

    /**
     * Status code (303) indicating that the response to the request can be
     * found under a different URI.
     */
    public static final int SC_SEE_OTHER = 303;

    /**
     * Status code (304) indicating that a conditional GET operation found that
     * the resource was available and not modified.
     */
    public static final int SC_NOT_MODIFIED = 304;

    /**
     * Status code (305) indicating that the requested resource <em>MUST</em> be
     * accessed through the proxy given by the <code><em>Location</em></code>
     * field.
     */
    public static final int SC_USE_PROXY = 305;

    /**
     * Status code (307) indicating that the requested resource resides
     * temporarily under a different URI. The temporary URI <em>SHOULD</em> be
     * given by the <code><em>Location</em></code> field in the response.
     */
    public static final int SC_TEMPORARY_REDIRECT = 307;

    /**
     * Status code (400) indicating the request sent by the client was
     * syntactically incorrect.
     */
    public static final int SC_BAD_REQUEST = 400;

    /**
     * Status code (401) indicating that the request requires HTTP
     * authentication.
     */
    public static final int SC_UNAUTHORIZED = 401;

    /**
     * Status code (402) reserved for future use.
     */
    public static final int SC_PAYMENT_REQUIRED = 402;

    /**
     * Status code (403) indicating the server understood the request but
     * refused to fulfill it.
     */
    public static final int SC_FORBIDDEN = 403;

    /**
     * Status code (404) indicating that the requested resource is not
     * available.
     */
    public static final int SC_NOT_FOUND = 404;

    /**
     * Status code (405) indicating that the method specified in the
     * <code><em>Request-Line</em></code> is not allowed for the resource
     * identified by the <code><em>Request-URI</em></code>.
     */
    public static final int SC_METHOD_NOT_ALLOWED = 405;

    /**
     * Status code (406) indicating that the resource identified by the request
     * is only capable of generating response entities which have content
     * characteristics not acceptable according to the accept headers sent in
     * the request.
     */
    public static final int SC_NOT_ACCEPTABLE = 406;

    /**
     * Status code (407) indicating that the client <em>MUST</em> first
     * authenticate itself with the proxy.
     */
    public static final int SC_PROXY_AUTHENTICATION_REQUIRED = 407;

    /**
     * Status code (408) indicating that the client did not produce a request
     * within the time that the server was prepared to wait.
     */
    public static final int SC_REQUEST_TIMEOUT = 408;

    /**
     * Status code (409) indicating that the request could not be completed due
     * to a conflict with the current state of the resource.
     */
    public static final int SC_CONFLICT = 409;

    /**
     * Status code (410) indicating that the resource is no longer available at
     * the server and no forwarding address is known. This condition
     * <em>SHOULD</em> be considered permanent.
     */
    public static final int SC_GONE = 410;

    /**
     * Status code (411) indicating that the request cannot be handled without a
     * defined <code><em>Content-Length</em></code>.
     */
    public static final int SC_LENGTH_REQUIRED =