Java Servlet 基础编程 HelloWorld & HelloForm

àì夳堔傛蜴生んèń 2022-04-25 02:54 175阅读 0赞

### 前言 ###

在工作的时候, 经常听别人说. `Servlet`是接触Web编程的第一步, 而不是`SSH`的框架编程. 由于, 在学校的网络编程的知识快忘了个干净. 本章 将两个基础的部分记录于此. 本章主要介绍`HttpServlet`的`Quick Start` Demo. 后一章主要介绍`表单提交`的Demo.

本章涉及的例子都可以在  
[https://github.com/SeanYanxml/arsenal/tree/master/arsenal-java/arsenal-servlet][https_github.com_SeanYanxml_arsenal_tree_master_arsenal-java_arsenal-servlet]  
下找到.

如果你觉得我的项目不错, 不妨给我一个Star. 你的支持就是我的动力.

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### 准备工作 ###

*  Java
 *  Eclipse IDE
 *  Maven
 *  Tomcat Server配置  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70]
 *  Maven依赖配置

<?xml version="1.0"?>
    <project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
      <modelVersion>4.0.0</modelVersion>
      <parent>
        <groupId>com.yanxml</groupId>
        <artifactId>arsenal-java-parent</artifactId>
        <version>0.0.1-SNAPSHOT</version>
      </parent>
      
      <groupId>com.yanxml</groupId>
      <artifactId>arsenal-servlet</artifactId>
      <version>0.0.1-SNAPSHOT</version>
      <name>arsenal-servlet</name>
      
      <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      </properties>
      
      <dependencies>
        
    	<dependency>
        	<groupId>javax.servlet</groupId>
        	<artifactId>javax.servlet-api</artifactId>
        	<version>4.0.0</version>
        	<scope>provided</scope>
    	</dependency>
      </dependencies>
    </project>

注: `Servlet 2.5+`在开发时, 经常使用`web.xml`进行相关的配置. 在`Servlet 3.0+`之后并不再使用其配置. 本章为还原经典配置, 仍然使用`web.xml`文件进行路由的配置.

--------------------

### 基本操作 ###

##### Case 1 HelloWorld #####

*  HelloWorld HttpServlet类

package com.yanxml.arsenal.servlet.hello;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class HelloWorldServlet extends HttpServlet{
    	
    	private String message;
    	
    	public void init() throws ServletException{
    		// 执行初始化操作
    		message = "Hello World.";
    	} 
    	
    	// Get 方法请求
    	public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException{
    		// 设置响应内容详情
    		response.setContentType("text/html");
    		
    		// 处理逻辑
    		PrintWriter writer = response.getWriter();
    		writer.print("<h1>"+message+"</h1>");
    	}
    	
    	public void destroy(){
    		// do nothing
    	}
    }

*  web.xml

<?xml version="1.0" encoding="UTF-8"?>  
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
        xmlns="http://java.sun.com/xml/ns/javaee"  
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"  
        id="WebApp_ID" version="3.0">  
        <display-name>ServletLearning</display-name>  
    
        <servlet>  
            <servlet-name>HelloWorld</servlet-name>  
            <servlet-class>com.yanxml.arsenal.servlet.hello.HelloWorldServlet</servlet-class>  
        </servlet>  
    
    	<servlet>
            <servlet-name>default</servlet-name>
            <servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
            <init-param>
                <param-name>debug</param-name>
                <param-value>0</param-value>
            </init-param>
            <init-param>
                <param-name>listings</param-name>
                <param-value>false</param-value>
            </init-param>
            <load-on-startup>1</load-on-startup>
        </servlet>
        
        <servlet-mapping>  
              
            <servlet-name>HelloWorld</servlet-name>  
            <url-pattern>/helloworld</url-pattern>  
        </servlet-mapping>  
        
        
        
        <servlet-mapping>
            <servlet-name>default</servlet-name>
            <url-pattern>/</url-pattern>
        </servlet-mapping>
    
    </web-app>

访问地址: [http://localhost:8080/arsenal-servlet/helloworld][http_localhost_8080_arsenal-servlet_helloworld]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 1]

##### Case 2 HelloForm #####

*  HelloFormServlet

import java.io.IOException;
    import java.io.PrintWriter;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    @WebServlet("/HelloForm")
    public class HelloFormServlet extends HttpServlet{
    	
    	public HelloFormServlet(){
    		super();
    	}
    	
    	protected void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{
    		response.setContentType("text/html;charset=UTF-8");
    		
    		PrintWriter writer = response.getWriter();
    		String title = "使用 GET 方法读取表单数据";
            // 处理中文
            String name =new String(request.getParameter("name").getBytes("ISO8859-1"),"UTF-8");
            String docType = "<!DOCTYPE html> \n";
            writer.println(docType +
                "<html>\n" +
                "<head><title>" + title + "</title></head>\n" +
                "<body bgcolor=\"#f0f0f0\">\n" +
                "<h1 align=\"center\">" + title + "</h1>\n" +
                "<ul>\n" +
                "  <li><b>站点名</b>："
                + name + "\n" +
                "  <li><b>网址</b>："
                + request.getParameter("url") + "\n" +
                "</ul>\n" +
                "</body></html>");
    	}
    	
    	public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException{
    		doGet(request, response);
    	}
    
    }

在类中使用`WebServlet`的方式进行配置, 避免了繁琐的`web.xml`配置.

*  hello.html 表单页面

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="utf-8">
    <title>Servlet教程</title>
    </head>
    <body>
    <form action="HelloForm" method="GET">
    网址名：<input type="text" name="name">
    <br />
    网址：<input type="text" name="url" />
    <input type="submit" value="提交" />
    </form>
    </body>
    </html>

值得注意的是 此处的`<form action="HelloForm" method="GET">`指定了此处需要提交链接的地址.

访问地址: [http://localhost:8080/arsenal-servlet/Hello.html][http_localhost_8080_arsenal-servlet_Hello.html]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 2]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 3]

--------------------

*  另: JSP与`Servlet`的区别.

一般使用JSP来实现页面. Servlet来实现业务逻辑.
    https://www.ppkao.com/tiku/shiti/8213672.html

[jsp与servlet的区别与联系][jsp_servlet]

--------------------

### Reference ###

\[1\]. [\[Runoob\]Servlet教程][Runoob_Servlet]

[https_github.com_SeanYanxml_arsenal_tree_master_arsenal-java_arsenal-servlet]: https://github.com/SeanYanxml/arsenal/tree/master/arsenal-java/arsenal-servlet
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70]: /images/20220210/a9db317997694fba9b245d573ce47291.png
[http_localhost_8080_arsenal-servlet_helloworld]: http://localhost:8080/arsenal-servlet/helloworld
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 1]: /images/20220210/419939119bbe472ebca4876e3ab5ff45.png
[http_localhost_8080_arsenal-servlet_Hello.html]: http://localhost:8080/arsenal-servlet/Hello.html
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 2]: /images/20220210/765be31788274a719f08c4c30f18b427.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 3]: /images/20220210/f60ec1309f1c4e63867da6877fb75ab7.png
[jsp_servlet]: https://www.cnblogs.com/sanyouge/p/7325656.html
[Runoob_Servlet]: http://www.runoob.com/servlet/servlet-intro.html