剛才看了幾篇對Servlet總結的文章,發現他們都有異曲同工之處,上來就是這樣寫的:
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Servlet三個要素:
1.必須繼承自HttpServlet
2.必須實現doGet()或者doPost()
3.必須在web.xml中配置Servlet
<servlet>
<servlet-name> </servlet-name>
<servlet-class> </servlet-class>
</servlet>
<servlet-mapping>
<servlet-name> </servlet-name>
<url-pattern> </url-pattern>
</servelt-mapping>
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有誰說了編寫一個Servlet必須繼承自HttpServlet類,必須實現doGet()或者doPost() ,難道實現Servlet接口就不行了嗎?
其實編寫一個Servlet主要有三種方法,一是實現Servlet接口,二是繼承抽象類GenericServlet,三是繼承HttpServlet類.下面分別用這三種方法去實現Servlet:
(一)要從實現Servlet接口來編寫一個Servlet是比較麻煩的,因為必須實現Servlet接口中的所有方法,Servlet接口主要定義了五個方法,它們分別為:
(1)void init(ServletConfig config) throws ServletException
(2)ServletConfig getServletConfig()
(3)void service(ServletRequest req,ervletResponse res) throws ServletException,IOException
(4)String getServletInfo()
(5)void destroy()
下面用實現Servlet接口的方法編寫一個Servlet:
import javax.servlet.*;
import java.io.*;
public class TestServlet implements Servlet
{
public void init(ServletConfig config) throws ServletException{
System.out.println("init");
}
public ServletConfig getServletConfig(){
reture null;
}
public void service(ServletRequest req,ServletResponse res)
throws ServletException,IOException{
//這里可以實現請求后要做的內容
PrintWriter out = response.getWriter();
out.println("Hello World!");
}
public String getServletInfo(){
return null;
}
public void destroy(){
System.out.println("destory");
}
}
(二)繼承抽象類GenericServlet編寫一個Serlvet,這個相對比實現Servlet接口要容易一點,GenericServlet類中只有一個抽象方法,即service(ServletRequest req, ServletResponse res),只要實現這個方法就行了,下面看例子:
import javax.servlet.*;
import java.io.IOException;
public TestGenericServlet extends GenericServlet{
public abstract void service(ServletRequest req,ServletResponse res)
throws ServletException,IOException{
PrintWriter out = response.getWriter();
out.println("Hello World!");
}
}
(3)繼承HttpServlet類編寫Servlet應該是最容易的,而且是最常見的,我們一般要編寫Servlet直接繼承這個類就行了,重寫doGet()或者doPost()方法即可,下面看例子:
import javax.servlet.http.*;
import javax.servlet.*;
import java.io.*;
public TestHttpServlet extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
response.setContentType("text/html;charset=gb2312");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<head>");
out.println("<title>HelloWorld</title>");
out.println("</head>");
out.println("<body bgcolor=\"white\">");
out.println("<hr>");
out.println("HelloWorld");
out.println("</body></html>");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
doGet(request, response);
}
}