第一个表单（Head first servlet+Jsp）（实验一）

第一个表单的HTML

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>BeerSel</title>
</head>
<body>
<h1 align="center">Beer Selection Page</h1>
<form method="POST" action="SelectBeer.do">
  Select beer charateristics<p>
  Color:
  <select name="color" size="1">
      <option value="light">light</option>
      <option value="amber">amber</option>
      <option value="brown">brown</option>
      <option value="dark">dark</option>
  </select>
  <br><br>
  <center>
     <input type="submit">
  </center>
</form>
</body>
</html>

2.在开发环境中创建DD

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>BeerSelect</display-name>
    <welcome-file-list>
    <welcome-file>form.jsp</welcome-file>
  </welcome-file-list>
  
  <servlet>
    <servlet-name>BeerSelect</servlet-name>
    <servlet-class>com.example.web.BeerSelect</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>BeerSelect</servlet-name>
    <url-pattern>/SelectBeer.do</url-pattern>
  </servlet-mapping>
</web-app>

3.控制器Servlet的第一版

package com.example.web;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class BeerSelect
 */
@WebServlet("/BeerSelect")
public class BeerSelect extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public BeerSelect() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		out.println("Beer Selection advice<br>");
		String c = request.getParameter("color");
		out.println("<br>got beer color:"+c);
	}

}

将项目添加至tomcat，启动tomcat。

在浏览器进行测试。

选择颜色后点击提交查询

改进这个servlet，让其调用模型

1.创建一个模型类

package com.example.model;

import java.util.ArrayList;
import java.util.List;

public class BeerExpert {
	public List getBrands(String color){
		List brands = new ArrayList();
		if(color.equals("amber")){
			brands.add("Jack Amber");
			brands.add("Red Moose");
		}
		else
		{
			brands.add("Jail Pale Ale");
			brands.add("Gout Stout");
		}
		return(brands);
	}

}

2.改进servlet

package com.example.web;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;

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 com.example.model.BeerExpert;

/**
 * Servlet implementation class BeerSelect
 */
@WebServlet("/BeerSelect")
public class BeerSelect extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public BeerSelect() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		String c = request.getParameter("color");
		BeerExpert be = new BeerExpert();
		List result = be.getBrands(c);
		
		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		out.println("Beer Selection advice<br>");
		
		Iterator it = result.iterator();
		while(it.hasNext())
		{
			out.println("<br>try:"+it.next());
		}
	}

}

测试效果

提交后

改进这个servlet，让其调用JSP返回

1.返回的JSP页面

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ page import="java.util.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Beer advice</title>
</head>
<body>
<h1 align="center">Beer Recomendations</h1>
<p>
<%
    List styles = (List)request.getAttribute("styles");
	Iterator it = styles.iterator();
	while(it.hasNext()){
	   out.print("<br>try:"+it.next());
	}
%>
</body>
</html>

2.改进后的Servlet

package com.example.web;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;

import javax.servlet.RequestDispatcher;
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 com.example.model.BeerExpert;

/**
 * Servlet implementation class BeerSelect
 */
@WebServlet("/BeerSelect")
public class BeerSelect extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public BeerSelect() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		String c = request.getParameter("color");
		BeerExpert be = new BeerExpert();
		List result = be.getBrands(c);
		
//		response.setContentType("text/html");
//		PrintWriter out = response.getWriter();
//		out.println("Beer Selection advice<br>");
		
//		Iterator it = result.iterator();
//		while(it.hasNext())
//		{
//			out.println("<br>try:"+it.next());
//		}
		request.setAttribute("styles", result);//为请求对象增加一个属性供JSP使用
		RequestDispatcher view = request.getRequestDispatcher("advice.jsp");
		//为JSP实例化一个请求分派器
		view.forward(request, response);//使用请求分派器要求容器准备好JSP，并向JSP发送请求和响应
	}

}

重新启动tomcat

测试结果：

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原文地址：https://www.cnblogs.com/zoeyqq/p/6834661.html