Servlet入门开发

http://host[:port]/[abs_path]

http://IP(主机名/域名):端口/访问的资源路径

<Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" />

java.util.logging.ConsoleHandler.encoding = GBK

package com.msb.testservlet;
/**
 * @Author: zhaoss
 */
public class Servlet01{

}

package com.msb.testservlet;

/**
 * @Author: zhaoss
 */
public class Servlet01 extends HttpServlet {

}

package com.msb.testservlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
public class Servlet01 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 控制台打印一句话
        System.out.println("hi servlet");
        // 响应一句话给浏览器
        resp.getWriter().write("hi servlet");
    }
}

package com.msb.testservlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/s01")
public class Servlet01 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 控制台打印一句话
        System.out.println("hi servlet");
        // 响应一句话给浏览器
        resp.getWriter().write("hi servlet");
    }
}

@WebServlet(name="Servlet01",value="/ser01")

@WebServlet(name="Servlet01",urlPatterns = "/ser01")

@WebServlet(name="Servlet01",value={"/ser01",'/ser001'})

@WebServlet(name="Servlet01",urlPatterns={"/ser01",'/ser001'})

package com.msb.testservlet;

import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/s01")
public class Servlet01 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 控制台打印一句话
        System.out.println("hi servlet");
        // 响应一句话给浏览器
        resp.getWriter().write("hi servlet");
    }

}

package com.msb.testservlet;

import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/s02")
public class Servlet02 extends GenericServlet {
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("servlet02...");
    }
}

package com.msb.testservlet;

import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/s03")
public class Servlet03 implements Servlet {

    @Override
    public void init(ServletConfig servletConfig) throws ServletException {

    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("servlet03...");
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }
}

package com.msb.testservlet;

import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/s01")
public class Servlet01 extends HttpServlet {
    //@Override
    /*protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 控制台打印一句话
        System.out.println("hi servlet");
        // 响应一句话给浏览器
        resp.getWriter().write("hi servlet");
    }*/

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("get...");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //System.out.println("post....");
        this.doGet(req,resp);//无论get请求和post请求都会走同一套业务逻辑。
    }
}

<?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">
    <servlet>
        <servlet-name>a</servlet-name>
        <servlet-class>com.msb.testservlet.Servlet04</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>a</servlet-name>
        <url-pattern>/s04</url-pattern>
    </servlet-mapping>
</web-app>

package com.msb.testservlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
public class Servlet04 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("servlet04");
    }
}

public void init(ServletConfig config) throws ServletException {
    System.out.println("实例创建了...");
}

protected void service(HttpServletRequest req, HttpServletResponse resp) 
    throws ServletException, IOException {
    System.out.println("服务调用了...");
}

public void destroy() {
	System.out.println("实例销毁了...");
}

public Servlet04() {
  	System.out.println("构造方法调用...");
}

package com.msb.testservlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/s05")
public class Servlet05 extends HttpServlet {
    public Servlet05(){
        System.out.println("构造器被调用了");
    }

    @Override
    public void init() throws ServletException {
        System.out.println("Servlet-init");
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("处理业务 ");
    }

    @Override
    public void destroy() {
        System.out.println("Servlet对象被销毁");
    }
}

4. 会构建HttpServletRequest 实现类对象、HttpServletResponse 实现类对象 ，处理请求和响应

// 获取客户端请求的完整URL （从http开始，到?前面结束）
String url = request.getRequestURL().toString();
System.out.println("获取客户端请求的完整URL：" + url);
//  获取客户端请求的部分URL （从站点名开始，到?前面结束）
String uri = request.getRequestURI();
System.out.println("获取客户端请求的部分URL：" + uri);
// 获取请求行中的参数部分
String queryString = request.getQueryString();
System.out.println("获取请求行中的参数部分：" + queryString);
// 获取客户端的请求方式
String method = request.getMethod();
System.out.println("获取客户端的请求方式：" + method);
// 获取HTTP版本号
String protocol = request.getProtocol();
System.out.println("获取HTTP版本号：" + protocol);
// 获取webapp名字 （站点名）
String webapp = request.getContextPath();
System.out.println("获取webapp名字：" + webapp);

// 获取指定名称的参数，返回字符串
String uname = request.getParameter("uname");
System.out.println("uname的参数值：" + uname);
// 获取指定名称参数的所有参数值，返回数组
String[] hobbys = request.getParameterValues("hobby");
System.out.println("获取指定名称参数的所有参数值：" + Arrays.toString(hobbys));

package com.msb.testrequest;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/sr02")
public class ServletRequest02 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String uname = req.getParameter("uname");
        System.out.println("接收到的uname参数为：" + uname);
    }
}

<%--
  Created by IntelliJ IDEA.
  User: zss
  Date: 2022/12/29
  Time: 12:56
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <form action="sr02" method="get">
        用户名：<input type="text" name="uname">
        <input type="submit" value="提交">
    </form>
</body>
</html>

new String(request.getParameter(name).getBytes("ISO-8859-1"),"UTF-8");

request.setCharacterEncoding("UTF-8");

request.getRequestDispatcher(url).forward(request,response);

<%--
  Created by IntelliJ IDEA.
  User: zss
  Date: 2022/12/29
  Time: 13:43
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <form action="sr03" method="post">
    用户名：<input type="text" name="uname">
    <input type="submit" value="登录">
  </form>
</body>
</html>

package com.msb.testrequest;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/sr03")
public class ServletRequest03 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取前台的表单传递过来的数据：
        String uname = req.getParameter("uname");
        System.out.println("浏览器传过来的数据uname的值：" + uname);
        // 请求转发到另一个Servlet:
        req.getRequestDispatcher("sr04").forward(req,resp);
        // 请求转发后输出一句话：
        System.out.println("------sr03");
    }
}

package com.msb.testrequest;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/sr04")
public class ServletRequest04 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取上一个Servlet传过来的数据：
        String uname = req.getParameter("uname");
        System.out.println("上一个Servlet传过来的数据uname的值：" + uname);
    }
}

package com.msb.testrequest;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/sr03")
public class ServletRequest03 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取前台的表单传递过来的数据：
        String uname = req.getParameter("uname");
        System.out.println("浏览器传过来的数据uname的值：" + uname);
        // 请求转发到另一个Servlet:
        req.getRequestDispatcher("index.jsp").forward(req,resp);
        // 请求转发后输出一句话：
        System.out.println("------sr03");
    }
}

package com.msb.testrequest;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/sr03")
public class ServletRequest03 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取前台的表单传递过来的数据：
        String uname = req.getParameter("uname");
        System.out.println("浏览器传过来的数据uname的值：" + uname);
        // 请求转发到另一个Servlet:
        //req.getRequestDispatcher("sr04").forward(req,resp);
        //req.getRequestDispatcher("index.jsp").forward(req,resp);
        req.getRequestDispatcher("http://www.baidu.com").forward(req,resp);
        // 请求转发后输出一句话：
        System.out.println("------sr03");
    }
}

// 设置域对象内容
request.setAttribute(String name, String value);
// 获取域对象内容
request.getAttribute(String name); 
// 删除域对象内容
request.removeAttribute(String name);

package com.msb.testrequest;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/msb/sr03")
public class ServletRequest03 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取前台传过来的数据：
        String uname = req.getParameter("uname");
        System.out.println("前台传到sr03-Servlet中的uname的数值为：" + uname);
        // 域对象数据的共享：
        req.setAttribute("age","18");
        String age = (String)req.getAttribute("age");
        System.out.println("servlet03---age:" + age);
        // 请求转发：
        req.getRequestDispatcher("/sr04").forward(req,resp);
        // 在请求转发以后输出一句话：
        System.out.println("-----sr03");
    }
}

package com.msb.testrequest;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/sr04")
public class ServletRequest04 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取请求数据：
        String uname = req.getParameter("uname");
        // 获取域对象中数据：
        String age = (String)req.getAttribute("age");
        System.out.println("servlet04---age:" + age);
        System.out.println("sr04-Servlet中获取uname的数值为：" + uname);
    }
}

// 响应数据：
        // PrintWriter字符输出流-获取字符流(只能响应回字符)
        resp.getWriter().write("hi01");//只能打印输出文本格式，不可以输出对象
        resp.getWriter().print("hi01");//可以输出对象

        // ServletOutputStream字节输出流-获取字节流(能响应一切数据)
        resp.getOutputStream().write("hi".getBytes());
        // 设置响应头,一般用于更新原来的响应头，key相同，后面设置的会覆盖前面设置的
        resp.setHeader("key1","value1");
        resp.setHeader("key1","value2");
        // 设置响应头,一般用于添加新的响应头，key不同，后面设置的不会覆盖前面设置的
        resp.addHeader("key3","value3");
        resp.addHeader("key3","value4");

package com.msb.testresponse;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/msb/sr02")
public class ServletResponse02 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().print("你好");
    }
}

response.setCharacterEncoding("UTF-8");

// 下面两行代码是等价的
response.setHeader("content-type", "text/html;charset=UTF-8");
response.setContentType("text/html;charset=UTF-8");

// 设置请求信息的解码格式：
req.setCharacterEncoding("UTF-8");
// 设置响应信息的编码格式：
resp.setCharacterEncoding("UTF-8");
// 设置浏览器的编码格式：
resp.setContentType("text/html;charset=UTF-8");

// 重定向跳转到index.jsp
response.sendRedirect("index.jsp");

package com.msb.testresponse;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/red1")
public class ServletResponse03 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取前台传过来的参数：
        String uname = req.getParameter("uname");
        System.out.println("前台传递过来的参数：" + uname);
        // 重定向：
        resp.sendRedirect("red2");
        // 重定向后打印一句话：
        System.out.println("---重定向后打印内容----");
    }
}

package com.msb.testresponse;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/red2")
public class ServletResponse04 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 看看是否能获取重定向过来的数据：
        String uname = req.getParameter("uname");
        System.out.println("是否可以获取到重定向过来的数据呢？--》" + uname);
    }
}

package com.msb.testresponse;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/red1")
public class ServletResponse03 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取前台传过来的参数：
        String uname = req.getParameter("uname");
        System.out.println("前台传递过来的参数：" + uname);
        // 重定向：
        resp.sendRedirect("http://www.baidu.com");
        // 重定向后打印一句话：
        System.out.println("---重定向后打印内容----");
    }
}

如果不需要:都可以