【正文】 y contains a number of the first, known as the HTTP request header. Provided the first body of information and request additional information sources. Some of the first is a standard, and some of the specific browser. A request may also contain information, such as, information form body can contain HTML content. In HTML form, click Submit button, the form to use ACTION = POST or ACTION = GET method, enter the contents of the form have been sent to the server. The contents of this form by POST method or GET method in the request to send the message body.Server to send request, return HTTP response. Have some structure to respond to each by the state to respond to the start line, may include a number of head and body of information may be known as the HTTP response headers and body to respond to information, the head and body of information sent by the server to the client browser, body of information that customers request the results page for the JSP page is static information pages. Users may have been familiar with the status line, status line shows the agreement is being used, status code and text messaging. For example, if a server request error, then return an error status line and error description, for example, HTTP/ 404 Object Not Found. If the server successfully responded to the request for the page is returned that contains 200 OK status line.HTTP munication protocol between a client and a server to submit (Request) information and respond to information (request / response) munication protocol. In the JSP, the builtin object request package of information submitted by the user, then the object can call the appropriate method to obtain the information package, the use of the object can get users to submit information. Builtin object request is a type of interface SerletRequest an example of Tomcat server in the webapps \ tomcatdocs \ servletapi to find ways to interface SerletRequest.When a customer visits a page the server will be submitted to an HTTP request, the server receives a request, the HTTP response to return. Response and a similar request, but also a structure, by each state to respond to the start line, may include a number of head and body may be information. With the corresponding request object is the target response. Response object can be used on the client39。s request for a dynamic response, send data to the client. For example, when a client requests access to a JSP page, the page with page directive settings page contentType attribute value is text / html, then the JSP attribute values of this engine will respond to customer requests on the page will be part of the page to return to the static to customers, the user39。s browser in response to receiving the HTML parser will be used to explain the implementation of the information received.HTTP protocol is a stateless protocol. A client request to the server (), and then the server returns in response to (), connection has been closed. Not to retain the serverside connection information, so next time to connect, the server has no previous connection information to be able to judge this time to connect and the former belong to the same connection is a client. When a customer visits a Web services directory may be in the directory server to connect a few pages again and repeated constantly refresh a page or to submit information on one page, the server should be some way to know that this is with a client. Tomcat server can use the builtin session (session) objects connect the relevant information recorded. Builtin session object created by the Tomcat server, session the HttpSession interface to achieve a kind of example, the Tomcat server in the webapps \ tomcatdocs \ servletapi search method HttpSession interface.We already know that when a customer39。s first visit to the Web services directory on a JSP page, JSP engine and the client to create a corresponding object of the session, when customers visit the various Web services directory browsing between pages, this session are the same object, and session objects of different clients is a separate one. With the session object is a different application object, the object created by the server, each Web services application directory service object was to visit the directory of users to share all the different Web services application directory different from each other.Out object is an output stream, used to output data to the client. Out object can call the following method has been applied to the output of various data, such as: (boolean), (boolean): output a boolean value. (char), (char): output a boolean value. (double), (double): output a boolean value. (float), (float): output a boolean value. (long), (long): output a boolean value. (String), (String): output a boolean value. (): output a newline. (): output buffer39。s content. (): close the stream.Println and print methods is the difference between: println to write a cache line, and the print is not written into the line. However, the browser display area is not currently written into the identification of the println line, if you want to show the line browser, it should be written to the browser wrap br achieve.37