1 实现Servlet
接口,然后实现接口中的五个方法,代码为:
public class Hello implements Servlet{
//该函数用于初始化servlet,类似于类的构造函数,该函数只会被调用一次
public void init(ServletConfig parm1) throws ServletException {
System.out.println("init it!");
}
public ServletConfig getServletConfig() {
// TODO: Add your code here
return null;
}
//这个函数用于处理业务逻辑
//当用户每访问servlet时,都会调用
//req:用于获得客户端(浏览器)信息
//res:用于向客户端(浏览器)返回信息
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
//从res中得到PrintWriter
System.out.println("Service it");
PrintWriter pw = res.getWriter();
pw.println("Hello world!");
}
public String getServletInfo() {
return "";
}
//销毁,释放内存,三种方式会触发destroy
//1. reload该servlet(webApps) 2. 关闭tomcat 3.关机
public void destroy() {
System.out.println("destroy it!");
}
}
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2 继承GenericServlet
,只需要实现一个方法:service
public class HelloGen extends GenericServlet{
//重写一个方法service即可
public void service(ServletRequest req, ServletResponse res){
//返回Hello world, generic
try{
PrintWriter pw = res.getWriter();
pw.println("Hello generic");
}
catch(Exception e){
e.printStackTrace();
}
}
}
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3 继承HttpServlet
,复写doGet
和doPost方法
public class HelloHttp extends HttpServlet{
//处理get请求
public void doGet(HttpServletRequest req, HttpServletResponse res){
//业务逻辑
try{
PrintWriter pw = res.getWriter();
pw.println("hello, Http");
}
catch (Exception e){
e.printStackTrace();
}
}
public void doPost(HttpServletRequest req, HttpServletResponse res){
this.doGet(req,res);
}
}
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当然,每次写好代码之后,需要在web.xml
中注册新的servlet
web.xml
:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="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_4_0.xsd"
version="4.0"
metadata-complete="true">
<display-name>Welcome to Tomcat</display-name>
<description>
Welcome to Tomcat
</description>
//第一种方式需要加入的部分
<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>com.thorin.Hello</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/thorin</url-pattern>
</servlet-mapping>
//第二种方式需要加入的部分
<servlet>
<servlet-name>hellogen</servlet-name>
<servlet-class>com.thorin.HelloGen</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>hellogen</servlet-name>
<url-pattern>/hellogen</url-pattern>
</servlet-mapping>
//第三种方式需要加入的部分
<servlet>
<servlet-name>hellohttp</servlet-name>
<servlet-class>com.thorin.HelloHttp</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>hellohttp</servlet-name>
<url-pattern>/hellohttp</url-pattern>
</servlet-mapping>
</web-app>