Servlet的使用方法详细说明

Servlet的生命周期方法：

init()
destroy()
doGet(HttpServletRequest request,HttpServletResponse response)
客户端请求封装在request中，而服务器响应则封装在response中

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web.xml的配置（有多个servlet就配置多个servlet 和servlet-mapping标签）

<servlet>
<servlet-name>Servelettest1</servlet-name>
<servlet-class>com.web.servlet.Servelettest1</servlet-class>  //全路径
</servlet>
<servlet-mapping>
<servlet-name>Servelettest1</servlet-name>
<url-pattern>/Servelettest1</url-pattern>                               //浏览请求别名，前面必须加斜杠
</servlet-mapping>

public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{

PrintWriter pw = response.getWriter();                              //这个输出流是从web服务器到浏览器，打印在web服务器中
pw.print("hello world");
pw.close();
}

public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException{
PrintWriter pw = response.getWriter();
pw.print("hello world");
pw.close();
}

在index.jsp中

<a href="./Servelettest1">hello world<a>
<form action="Servelettest1" method="post">     //Servelettest1是 <url-pattern>/Servelettest1</url-pattern>
<input type="submit" value="提交">

http://localhost:8088/Servelettest1 //Servelettest1是 <url-pattern>/Servelettest1</url-pattern>
http://localhost:8088/index.jsp
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使用request和response
response.getWriter();
//获取客户机参数方法
request.getParameter("username "); //获取参数 index.jsp对应代码段为<a href="Servelettest1?username=boyce">hello world<a>
servlet接受请求封装信息:

public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException{
String username = request.getParameter("username");                                          //获取用户名
String password = request.getParameter("password");
PrintWriter pw = response.getWriter();
pw.print("hello world"+username+password);
pw.close();
}

对应jsp:

<form action="Servelettest1" method="post">
用户账号：<input type="text" name="username">
用户密码：<input type="password" name="password">
<input type="submit" value="提交">
</form>

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server.xml: //从客户端到服务器的中文乱码

<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000" URIEncoding="utf-8"
redirectPort="8443" />

遇到server.xml拒绝访问解决方法：



进去选择编辑，然后选择user权限勾选完全控制即可



//从服务器到客户端的中文乱码
response.setCharacterEncoding("utf-8");
response.setContentType(text/html;charset=utf-8)

servlet实现页面跳转：

package com.web.servlet;

import java.io.IOException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servelettest2 extends HttpServlet{
public void init(){

}
public void destroy(){
}
public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException{
String uname = request.getParameter("username");
String password = request.getParameter("password");
System.out.println("Servelet2被调用");
//页面跳转
response.sendRedirect("Servelettest3");                                                    //实现页面的跳转
}
}

方法二:

RequestDispatcher rd = request.getRequestDispatcher("Servelettest3");
rd.forward(request,response);

index.jsp：

<form action="Servelettest2" method="post">
用户账号：<input type="text" name="username">
用户密码：<input type="password" name="password">
<input type="submit" value="提交">
</form>

doPost中文乱码解决：

public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException{
request.setCharacterEncoding("UTF-8");                                        //解决请求服务器中文乱码
response.setCharacterEncoding("UTF-8");                                     //解决服务器到客户端乱码问题
response.setContentType("text/html; charset=utf-8");                  //解决服务器到客户端乱码问题
String username = request.getParameter("username");
String password = request.getParameter("password");
PrintWriter pw = response.getWriter();
pw.print("hello world"+username+password);
System.out.println(username+password);
pw.close();
}

过滤器:

<filter>
<filter-name>/filter1</filter-name>
<filter-class>com.web.servlet.CharacterFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>/filter1</filter-name>
<url-pattern>/*</url-pattern>                                                       //星号代表所有的传输都要经过它
</filter-mapping>

package com.web.servlet;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class CharacterFilter implements Filter{

@Override
public void destroy() {
// TODO Auto-generated method stub

}

@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
throws IOException, ServletException {
// TODO Auto-generated method stub
arg0.setCharacterEncoding("utf-8");
arg1.setCharacterEncoding("utf-8");
arg1.setContentType("text/html; charset=utf-8");
arg2.doFilter(arg0, arg1);

}

@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub

}

}

监听器：
servlet中定义了多种类监听器，它们主要用于监听ServletContext,HttpSession和ServletRequest这三个域对象：

HttpSessionListener接口用于监听HttpSession的创建与销毁

（1）创建一个Session时，sessionCreated(HttpSessionEvent se)方法将会被调用。
（2）销毁一个Session时，sessionDestroy(HttpSessionEvent se)方法将会被调用。
Session域对象创建和销毁时机
创建：yoghurt第一次访问时，服务器创建session
销毁:如果用户30分钟会使用，服务器将会销毁session，我们在web.xml里面也可以诶之session失效时间

<session-config>
<session-timeout>1</session-timeout>            //设置监听时长为一分钟，若不修改，默认为30分钟
</session-config>

package com.web.servlet;

import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
//实现接口HttpSessionListener
public class OnlineCounterListener implements HttpSessionListener,HttpSessionAttributeListener{

private int count=0;
@Override
public void sessionCreated(HttpSessionEvent arg0) {
// TODO Auto-generated method stub
count++;
System.out.println("有新用户访问，当前访问人数为："+count);
}

@Override
public void sessionDestroyed(HttpSessionEvent arg0) {
// TODO Auto-generated method stub
count--;
System.out.println("有一位退出，当前人数为："+count);

}

@Override
public void attributeAdded(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub

}

@Override
public void attributeRemoved(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub

}

@Override
public void attributeReplaced(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub

}

}

总结：
servlet步骤
1.创建servlet类（继承于HttpServlet）
2.三个方法：public void init() {

}

public void destroy() {
}

public void doPost(HttpServletRequest request, HttpServletResponse response){
}
3.通过getParameter 获取jsp中的值
String username = request.getParameter("username");
4.然后调用jdbc或Hibernate类（Dao）将对象进行增删查改
5.跳转页面
// 转发到注册结果页面
request.getRequestDispatcher("result.jsp").forward(request, response);