web服务器接收到客户端的Http请求，针对这个请求，会分别创建一个代表请求的HttpServletRequest对象，代表响应的一个HttpServletResponse；
- 如果要获取客户端请求过来的参数：找HttpServletRequest
- 如果要给客户端响应一些信息：找HttpServletResponse
简单分类
负责向浏览器发送数据的方法
public ServletOutputStream getOutputStream() throws IOException;
public PrintWriter getWriter() throws IOException;
负责向浏览器发送响应头的方法
public void setCharacterEncoding(String charset);
public void setContentLength(int len);
public void setContentLengthLong(long len);
public void setContentType(String type);
public void setDateHeader(String name, long date);
响应的状态码
/**
* 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 = 411;
/**
* Status code (412) indicating that the precondition given in one
* or more of the request-header fields evaluated to false when it
* was tested on the server.
*/
public static final int SC_PRECONDITION_FAILED = 412;
/**
* Status code (413) indicating that the server is refusing to process
* the request because the request entity is larger than the server is
* willing or able to process.
*/
public static final int SC_REQUEST_ENTITY_TOO_LARGE = 413;
/**
* Status code (414) indicating that the server is refusing to service
* the request because the <code><em>Request-URI</em></code> is longer
* than the server is willing to interpret.
*/
public static final int SC_REQUEST_URI_TOO_LONG = 414;
/**
* Status code (415) indicating that the server is refusing to service
* the request because the entity of the request is in a format not
* supported by the requested resource for the requested method.
*/
public static final int SC_UNSUPPORTED_MEDIA_TYPE = 415;
/**
* Status code (416) indicating that the server cannot serve the
* requested byte range.
*/
public static final int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
/**
* Status code (417) indicating that the server could not meet the
* expectation given in the Expect request header.
*/
public static final int SC_EXPECTATION_FAILED = 417;
/**
* Status code (500) indicating an error inside the HTTP server
* which prevented it from fulfilling the request.
*/
public static final int SC_INTERNAL_SERVER_ERROR = 500;
/**
* Status code (501) indicating the HTTP server does not support
* the functionality needed to fulfill the request.
*/
public static final int SC_NOT_IMPLEMENTED = 501;
/**
* Status code (502) indicating that the HTTP server received an
* invalid response from a server it consulted when acting as a
* proxy or gateway.
*/
public static final int SC_BAD_GATEWAY = 502;
/**
* Status code (503) indicating that the HTTP server is
* temporarily overloaded, and unable to handle the request.
*/
public static final int SC_SERVICE_UNAVAILABLE = 503;
/**
* Status code (504) indicating that the server did not receive
* a timely response from the upstream server while acting as
* a gateway or proxy.
*/
public static final int SC_GATEWAY_TIMEOUT = 504;
/**
* Status code (505) indicating that the server does not support
* or refuses to support the HTTP protocol version that was used
* in the request message.
*/
public static final int SC_HTTP_VERSION_NOT_SUPPORTED = 505;
常见应用
1.向浏览器输出消息
2.下载文件
- 获取下载文件的路径
- 获取下载的文件名
- 设置想办法让浏览器能够支持下载我们需要的东西
- 获取下载文件的输入流
- 创建缓冲区
- 获取OutputStream对象
- 将FileOutputStream流写入到buffer缓冲区
- 使用OutputStream将缓冲区中的数据输出到客户端
// 下载文件的路径：D:\JavaEnvironment\apache-tomcat-7.0.68\webapps\resp\wip.jpg
// 下载文件的路径：D:\javaweb-02-servlet\response\target\classes\wip.jpg
// + 获取下载文件的路径
// String realPath = this.getServletContext().getRealPath("/wip.jpg");
String realPath = "D:\\javaweb-02-servlet\\response\\target\\classes\\测试.jpg";
System.out.println("下载文件的路径：" + realPath);
// + 获取下载的文件名
String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
// + 设置想办法让浏览器能够支持下载我们需要的东西
resp.setHeader("Content-disposition","attachment;filename="+ URLEncoder.encode(fileName,"UTF-8"));
// + 获取下载文件的输入流
FileInputStream fileInputStream = new FileInputStream(realPath);
// + 创建缓冲区
int len = 0;
byte[] buffer = new byte[1024];
// + 获取OutputStream对象
ServletOutputStream outputStream = resp.getOutputStream();
// + 将FileOutputStream流写入到buffer缓冲区
while ((len = fileInputStream.read(buffer)) > 0) {
outputStream.write(buffer,0,len);
}
// + 使用OutputStream将缓冲区中的数据输出到客户端
fileInputStream.close();
outputStream.close();