javaWEB總結(7):HttpServlet和HttpServletRequest__java

前言:HttpServletRequest對象封裝了用戶端進行HTTP協議請求時的所有資訊，HttpServletRequest繼承了ServletRequest，所以和ServletRequest一樣，是由tomcat伺服器提供實現的。具體過程如下:

1）Web客戶向Servlet容器發出Http請求；

2）Servlet容器解析Web客戶的Http請求；

3）Servlet容器建立一個HttpRequest對象，在這個對象中封裝Http請求資訊；

1.HttpServlet

說到HttpServletRequest就不得不說一下HttpServlet,下面看它的API:

javax.servlet.http
Class HttpServlet

java.lang.Object  javax.servlet.GenericServlet      javax.servlet.http.HttpServlet

All Implemented Interfaces: Serializable, Servlet, ServletConfig

Method Summary
protected  void	doDelete(HttpServletRequest req,HttpServletResponse resp)           Called by the server (via the service method) to allow a servlet to handle a DELETE request.
protected  void	doGet(HttpServletRequest req,HttpServletResponse resp)           Called by the server (via the service method) to allow a servlet to handle a GET request.
protected  void	doHead(HttpServletRequest req,HttpServletResponse resp)           Receives an HTTP HEAD request from the protected service method and handles the request.
protected  void	doOptions(HttpServletRequest req,HttpServletResponse resp)           Called by the server (via the service method) to allow a servlet to handle a OPTIONS request.
protected  void	doPost(HttpServletRequest req,HttpServletResponse resp)           Called by the server (via the service method) to allow a servlet to handle a POST request.
protected  void	doPut(HttpServletRequest req,HttpServletResponse resp)           Called by the server (via the service method) to allow a servlet to handle a PUT request.
protected  void	doTrace(HttpServletRequest req,HttpServletResponse resp)           Called by the server (via the service method) to allow a servlet to handle a TRACE request.
protected  long	getLastModified(HttpServletRequest req)           Returns the time the HttpServletRequest object was last modified, in milliseconds since midnight January 1, 1970 GMT.
protected  void	service(HttpServletRequest req,HttpServletResponse resp)           Receives standard HTTP requests from the public service method and dispatches them to thedoXXX methods defined in this class.
void	service(ServletRequest req,ServletResponse res)           Dispatches client requests to the protected service method.

可以看到HttpServlet實現了servlet介面，所以其中的 service(ServletRequest req,ServletResponse res)方法和servlet中的一致，在每次請求時調用。只抽取部分方法，概要資訊如下:

(1).doGet(HttpServletRequest req,HttpServletResponse resp):接收HTTP的GET請求；

(2).doPost(HttpServletRequest req,HttpServletResponse resp):接收HTTP的POST請求；

(3).service(HttpServletRequest req,HttpServletResponse resp):接收HTTP請求，並把它分配到doXXX方法中；

2.HttpServletRequest的API:

javax.servlet.http
Interface HttpServletRequest All Superinterfaces: ServletRequest All Known Implementing Classes: HttpServletRequestWrapper

String	getAuthType()           Returns the name of the authentication scheme used to protect the servlet.
String	getContextPath()           Returns the portion of the request URI that indicates the context of the request.
Cookie[]	getCookies()           Returns an array containing all of the Cookie objects the client sent with this request.
long	getDateHeader(String name)           Returns the value of the specified request header as a long value that represents aDate object.
String	getHeader(String name)           Returns the value of the specified request header as a String.
Enumeration	getHeaderNames()           Returns an enumeration of all the header names this request contains.
Enumeration	getHeaders(String name)           Returns all the values of the specified request header as an Enumeration ofString objects.
int	getIntHeader(String name)           Returns the value of the specified request header as an int.
String	getMethod()           Returns the name of the HTTP method with which this request was made, for example, GET, POST, or PUT.
String	getPathInfo()           Returns any extra path information associated with the URL the client sent when it made this request.
String	getPathTranslated()           Returns any extra path information after the servlet name but before the query string, and translates it to a real path.
String	getQueryString()           Returns the query string that is contained in the request URL after the path.
String	getRemoteUser()           Returns the login of the user making this request, if the user has been authenticated, ornull if the user has not been authenticated.
String	getRequestedSessionId()           Returns the session ID specified by the client.
String	getRequestURI()           Returns the part of this request's URL from the protocol name up to the query string in the first line of the HTTP request.
StringBuffer	getRequestURL()           Reconstructs the URL the client used to make the request.
String	getServletPath()           Returns the part of this request's URL that calls the servlet.
HttpSession	getSession()           Returns the current session associated with this request, or if the request does not have a session, creates one.
HttpSession	getSession(boolean create)           Returns the current HttpSession associated with this request or, if there is no current session andcreate is true, returns a new session.
Principal	getUserPrincipal()           Returns a java.security.Principal object containing the name of the current authenticated user.
boolean	isRequestedSessionIdFromCookie()           Checks whether the requested session ID came in as a cookie.
boolean	isRequestedSessionIdFromUrl()           Deprecated. As of Version 2.1 of the Java Servlet API, useisRequestedSessionIdFromURL() instead.
boolean	isRequestedSessionIdFromURL()           Checks whether the requested session ID came in as part of the request URL.
boolean	isRequestedSessionIdValid()           Checks whether the requested session ID is still valid.
boolean	isUserInRole(String role)           Returns a boolean indicating whether the authenticated user is included in the specified logical "role".

這裡只列舉常用的幾個方法(有些API中沒有列舉到的，是在ServletRequest中已有的方法):

(1)獲得客戶機資訊                                                                       

getRequestURL():返回用戶端發出請求時的完整URL。
getRequestURI():返回請求行中的資源名部分。
getQueryString() :返回請求行中的參數部分。
getRemoteAddr():返回傳出請求的客戶機的IP地址。
getRemoteHost() :返回傳出請求的客戶機的完整主機名稱。
getRemotePort():返回客戶機所使用的網路連接埠號碼。
getLocalAddr() :返回WEB伺服器的IP地址。
getLocalName():返回WEB伺服器的主機名稱。

(2)獲得客戶機要求標頭                                                                    

getHeaders(String name):獲得要求標頭資訊組成的Enumeration。

(3)獲得客戶機請求參數(用戶端提交的資料)