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Pick up Note 15.
1. Whether <%%> in JSP or <%\=%> will eventually be in the servlet's method body, is there an element that can be declared as a member of a class?
The answer is yes, and very very simple, this element is <%!%>, and we use it to solve the problem in note 15, just add an exclamation mark on the original basis.
Import= "sample.counter"%><%@ page contenttype= "Text/html;charset=utf-8" language= "java"%>< html><%! int count = 0; %><p>the page count is: </p><%= ++count%></body>2, we can also add the class member method in the exclamation mark.
JSP implicit object (built-in object)1, out is not the only JSP built-in Object!
What is a JSP built-in object? Essentially, all of the JSP built-in objects will eventually be mapped to something in the Servlet/jsp API.
For example, the built-in object request is essentially a mapping of the service's parameter httpservletrequest.
2. Textbook Practice
Index.html
<!DOCTYPE HTML><HTMLLang= "en"><Head> <MetaCharSet= "UTF-8"> <title></title></Head><Body><formAction= "Hobbypage.do"Method= "POST"> <P>Choose a hobby:</P> <Selectname= "Hobby"ID=""size= "1"> <optionvalue= "reading">Reading</option> <optionvalue= "Glory of the King">Play The Glory of Kings</option> <optionvalue= "Write code">Write code</option> <optionvalue= "Water Group">Water Group</option> </Select> <BR/> <inputtype= "Submit"></form></Body></HTML>Xml
<?XML version= "1.0" encoding= "UTF-8"?><Web-appxmlns= "Http://xmlns.jcp.org/xml/ns/javaee"Xmlns:xsi= "Http://www.w3.org/2001/XMLSchema-instance"xsi:schemalocation= "Http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"version= "3.1"> <servlet> <Servlet-name>Hi</Servlet-name> <Servlet-class>Sample.addfriends</Servlet-class> </servlet> <servlet-mapping> <Servlet-name>Hi</Servlet-name> <Url-pattern>/hobbypage.do</Url-pattern> </servlet-mapping></Web-app>Addfriends.java
PackageSample;ImportJavax.servlet.RequestDispatcher;Importjavax.servlet.ServletException;ImportJavax.servlet.http.HttpServlet;Importjavax.servlet.http.HttpServletRequest;ImportJavax.servlet.http.HttpServletResponse;Importjava.io.IOException;Importjava.util.ArrayList;Importjava.util.List; Public classAddfriendsextendsHttpServlet {@Overrideprotected voidDoPost (httpservletrequest req, HttpServletResponse resp)throwsservletexception, IOException {req.setcharacterencoding ("Utf-8"); List names=NewArrayList (); Names.add ("Fred"); Names.add ("Pradeep"); Names.add ("Philippe");Req.setattribute ("Names", names); RequestDispatcher View= Req.getrequestdispatcher ("result.jsp"); View.forward (req, resp); }}result.jsp
<%@ pageImport= "Java.util.List"%><%@ pageImport= "Java.util.Iterator"%><%--Created by IntelliJ. USER:XKFX Date:2017/6/14Time :17:27 to change ThisTemplate Use File | Settings |File Templates.--%><%@ page contenttype= "Text/html;charset=utf-8" language= "java"%>//response.setcharacterencoding ("Utf-8");%> <p>hello i ' m result</p> <p>the friends who share your hobby <%=request.getparameter ("Hobb Y ")%> is:</p> <%List Names= (List) request.getattribute ("names"); Iterator it=Names.iterator (); while(It.hasnext ()) {out.println (It.next () )+ "<br/>"); } %></body>Write about the two extreme pits that the problem encounters:
- In HTML, the argument to submit is value, not text! More details can be found here: Java Web development servlet Get form values
- To eventually get the HTML display in Chinese, neither in Addfriends.java resp.setcharacterencoding ("Utf-8"); Nor in the result.jsp response.setcharacterencoding ("Utf-8"); But in the Addfriends.java req.setcharacterencoding ("Utf-8");
"Head first Servlets and JSP" Note 16:jsp implicit objects (built-in objects)
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