JavaWeb-基础

转载

mb5fe55bba5ad74 2021-08-16 00:18:00

文章标签 java xml ide maven jar包 文章分类 Java 后端开发

Tomcat

目录结构

|--bin      脚本目录
|--conf     配置
|--lib      依赖的jar包
|--logs     日志
|--temp     临时文件
|--webapps  存放应用程序
|--work     工作目录

\conf\server.xml 配置

配置默认端口号

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

配置host

      <Host name="localhost"  appBase="webapps"
            unpackWARs="true" autoDeploy="true">

web目录结构

|--webapps
	|--root
	|--test
		|--index.html     目录首页
		|--WEB-INF
			|--classes    java程序
			|--lib        web所依赖的jar包
			|--web.xml    网站配置文件

Maven

在Java web开发中，需要使用大量的jar包，Maven能够自动导入和配置jar包。

Maven项目构架管理工具规定了目录配置核心：约定大于配置

配置

配置环境变量

JavaWeb-基础_maven

JavaWeb-基础_jar包_02

配置镜像

maven下的conf\settings.xml

在里面添加

<mirror>
    <id>nexus-aliyun</id>
    <mirrorOf>*</mirrorOf>
    <name>Nexus aliyun</name>  				  			<url>http://maven.aliyun.com/nexus/content/groups/public</url>
</mirror>

JavaWeb-基础_maven_03

配置本地仓库

<localRepository>E:\java\apache-maven-3.8.1\local-repo</localRepository>

JavaWeb-基础_java_04

配置IDEA

JavaWeb-基础_maven_06

JavaWeb-基础_maven_07

再重新创建项目就是一个干净的maven项目了

JavaWeb-基础_jar包_08

配置tomcat

JavaWeb-基础_java_09

JavaWeb-基础_java_10

JavaWeb-基础_maven_11

运行程序

JavaWeb-基础_ide_12

Servlet

Servlet就是sun公司开发动态web的一门技术
Sun在这些API中提供一个接口叫做: Servlet，如果你想开发一个Servlet程序，只需要完成两个小步骤;
编写一个类，实现Servlet接口
把开发好的Java类部署到web服务器中。
把实现了Servlet接口的Java程序叫做Servlet

创建servlet工程

配置pom.xml

    <dependencies>
        <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.3.3</version>
            <scope>provided</scope>
        </dependency>

    </dependencies>

当前工程就是Maven的主工程

新建Module

JavaWeb-基础_xml_13

优化Maven

配置最新的web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="4.0"
         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"
         metadata-complete="true">

</web-app>

搭建完整结构

JavaWeb-基础_java_14

HelloServlet

编写一个普通类

实现Servlet接口，继承自HttpServlet

package com.th0r.servlet;

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

public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        PrintWriter writer = resp.getWriter();
        writer.println("Hello Servlet");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

编写Servlet的映射

JAVA程序使用浏览器访问，需要在web服务中注册Servlet，还需要给出访问路径

  <!-- 注册Servlet-->
  <servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>com.th0r.servlet.HelloServlet</servlet-class>
  </servlet>
  <!-- Servlet请求的路径-->
  <servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>

配置tomcat

在添加Artfact时如果没有显示Application context 重新打开IDEA
运行

原理

借用网上的一张图

JavaWeb-基础_jar包_18

Mapping

一个Servlet可以指定一个映射路径

<servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
</servlet-mapping>

一个Servlet可以指定多个映射路径

<servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello1</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello2</url-pattern>
</servlet-mapping>

一个Servlet可以指定通用映射路径

<servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello/*</url-pattern>
</servlet-mapping>

默认请求路径

<servlet-mapping>
	<servlet-name>hello</servlet-name>
	<url-pattern>/*</url-pattern>
</servlet-mapping>

指定后缀或前缀

<servlet-mapping>
	<servlet-name>hello</servlet-name>
	<url-pattern>/*.qingjiag</url-pattern>
</servlet-mapping>

*前面不能加项目映射路径

指定了固有的映射路径优先级最高，如果找不到就会走默认的处理请求

ServletContext

共享数据

ServletContext官方叫servlet上下文。服务器会为每一个工程创建一个对象，这个对象就是ServletContext对象。这个对象全局唯一，而且工程内部的所有servlet都共享这个对象。所以叫全局应用程序共享对象。

JavaWeb-基础_xml_19

HelloServlet

package com.th0r.servlet;

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

public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();

        String uname = "root";
        context.setAttribute("uname", uname);

        System.out.printf("hello");

    }
}

GetServlet

package com.th0r.servlet;

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

public class GetServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();

        String uname = (String)context.getAttribute("uname");
        resp.getWriter().println("GetServlet: " + uname);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

JavaWeb-基础_ide_20

获取初始化参数

web.xml

  <context-param>
    <param-name>db</param-name>
    <param-value>jdbc:mysql://localhost:3306/mybatis</param-value>
  </context-param>

  <servlet>
    <servlet-name>db</servlet-name>
    <servlet-class>com.th0r.servlet.Demo1</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>db</servlet-name>
    <url-pattern>/db</url-pattern>
  </servlet-mapping>

demo1.java

package com.th0r.servlet;

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

public class Demo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        ServletContext context = this.getServletContext();
        String db = context.getInitParameter("db");
        resp.getWriter().println(db);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

JavaWeb-基础_jar包_21

请求转发

web.xml

  <servlet>
    <servlet-name>rd</servlet-name>
    <servlet-class>com.th0r.servlet.Demo2</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>rd</servlet-name>
    <url-pattern>/rd</url-pattern>
  </servlet-mapping>

Demo2

package com.th0r.servlet;

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

public class Demo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        ServletContext context = this.getServletContext();
        RequestDispatcher reqDis = context.getRequestDispatcher("/db");
        reqDis.forward(req,resp);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

JavaWeb-基础_ide_22

读取文件资源

Properties

java目录下的.peoperties/.xml
recourse目录下的.properties/.xml

都打包在了同一个路径下：classes 俗称 classpath

Demo3

package com.th0r.servlet;

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

public class Demo3 extends HttpServlet {
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        InputStream is = this.getServletContext().getResourceAsStream("/WEB-INF/classes/prop.properties");

        Properties prop = new Properties();
        prop.load(is);
        String username = prop.getProperty("username");
        String password = prop.getProperty("password");

        resp.getWriter().println(username + ": " + password);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

JavaWeb-基础_ide_23

本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。

上一篇：Java基础-注解与反射

下一篇：JavaWeb-Cookie和Session

提问和评论都可以，用心的回复会被更多人看到评论

发布评论

相关文章

官方博客	全部文章	热门标签	班级博客
了解我们	网站地图	意见反馈

鸿蒙开发者社区	51CTO学堂
51CTO	软考资讯

JavaWeb-基础

JavaWeb-基础

目录结构

web目录结构

配置

配置环境变量

配置镜像

配置本地仓库

配置IDEA

配置tomcat

创建servlet工程

配置pom.xml

新建Module

优化Maven

HelloServlet

原理

Mapping

ServletContext

共享数据

获取初始化参数

请求转发

读取文件资源

51CTO博客