初识JavaWeb

技术2026-04-13 10

初识JavaWeb

1.Tomcat

Tomcat 技术先进、性能稳定，而且免费，因而深受Java 爱好者的喜爱并得到了部分软件开发商的认可，成为目前比较流行的***Web 应用服务器。***

本地url请求过程

目录结构

bin目录下为一些可执行文件等等

webapps为存放网站的文件

网站的基本结构

2.Maven

Maven提供高级项目管理工具。由于 Maven 的缺省构建规则有较高的可重用性，所以常常用两三行 Maven 构建脚本就可以构建简单的项目。

目录结构

maven_repo为架包

阿里云镜像的配置

<mirror> <id>alimaven</id> <name>aliyun maven</name> <url>http://maven.aliyun.com/nexus/content/groups/public/</url> <mirrorOf>central</mirrorOf> </mirror>

3.Tomcat和Maven的下载

官网下载

4.IDEA中的创建Maven与配置Tomcat

5.HelloWorld

pom.xml配置

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>org.example</groupId> <artifactId>com</artifactId> <version>1.0-SNAPSHOT</version> <modules> <module>com.csn.serverlet</module> </modules> <packaging>pom</packaging> <name>com Maven Webapp</name>  <url>http://www.example.com</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>1.7</maven.compiler.source> <maven.compiler.target>1.7</maven.compiler.target> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.1.0</version> </dependency> <dependency> <groupId>javax.servlet.jsp</groupId> <artifactId>javax.servlet.jsp-api</artifactId> <version>2.3.3</version> </dependency> </dependencies> </project>

dependencies中放的很多的dependency都是架包，可以在maven官网上搜索导入

在main目录下创建java和resources文件夹

创建helloworld.java

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 helloWorld extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.setContentType("text/html"); resp.setCharacterEncoding("utf-8"); PrintWriter out = resp.getWriter(); out.println("<html>"); out.println("<head>"); out.println("<title>Hello CSN!</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Hello CSN!</h1>"); out.println("</body>"); out.println("</html>"); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }

注意此时已经jsp和servlet架包已经导入maven

配置web.xml

配置xml实现从web服务器到java文件的映射

<?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" metadata-complete="true"> <display-name>Welcome to Tomcat</display-name> <description> Welcome to Tomcat </description> <servlet> <servlet-name>CSNTEST</servlet-name> <servlet-class>helloWorld</servlet-class>//这里是关键，指向目标java文件 </servlet> <servlet-mapping> <servlet-name>CSNTEST</servlet-name> <url-pattern>/hellocsn2</url-pattern>//这里是路由地址，即浏览器访问的url地址 </servlet-mapping> </web-app>

6.pom.xml的继承

我们可以在根目录下创建一个新的maven项目，此时maven继承于父maven，各种架包无需重复导入，大大提升开发效率

7.ServletContext

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。***

1.共享数据

在一个servlet中保存数据，可以在另一个servlet中获取

存数据

package com.csn.servelet; 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 servletDemo04_1 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ServletContext context=this.getServletContext(); context.setAttribute("username","小陈"); resp.setContentType("text/html"); resp.setCharacterEncoding("utf-8"); resp.getWriter().print("<h1>设置字段成功</h1>"); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }

取数据

package com.csn.servelet; 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 servletDemo04 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ServletContext context=this.getServletContext(); String username=(String)context.getAttribute("username"); resp.setContentType("text/html"); resp.setCharacterEncoding("utf-8"); resp.getWriter().print("名字:"+username); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }

2.获得初始化参数

在web.xml中定义初始化参数

<?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" metadata-complete="true"> <context-param> <param-name>url</param-name> <param-value>jdbc:mysql://localhost:3306/myhabits</param-value> </context-param> </web-app>

读数据

package com.csn.servelet; 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 servletContext extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ServletContext context=this.getServletContext(); String url=context.getInitParameter("url"); resp.setContentType("text/html"); resp.setCharacterEncoding("utf-8"); resp.getWriter().print(url); } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } }

3.请求转发

不同于重定位

package com.csn.servelet; 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 servletDemo03 extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ServletContext context=this.getServletContext(); context.getRequestDispatcher("/servletcontext").forward(req,resp); } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } }

4.读取资源文件

在resource下建立一个db.properties文件，里面写上信息

然后将其读出

package com.csn.servelet; 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; import java.io.InputStream; import java.util.Properties; public class servletDemo05 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { InputStream is =this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties"); Properties prop=new Properties(); prop.load(is); String username=prop.getProperty("username"); String pwd=prop.getProperty("pwd"); resp.getWriter().print(username+":"+pwd); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }

在java目录下建立一个db.properties文件，里面写上信息

然后将其读出

需要注意如果直接点生成，java文件夹中的properties的文件会被过滤掉

因此需要在子pom.xml中配置

<build> <resources> <resource> <directory>src/main/resources</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>true</filtering> </resource> <resource> <directory>src/main/java</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>true</filtering> </resource> </resources> </build>

此时在执行后就会在tatget的java目录下生成properties文件

然后再通过servlet访问

package com.csn.servelet; 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 servletDemo06 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { InputStream is =this.getServletContext().getResourceAsStream("/WEB-INF/classes/com/csn/servelet/db.properties"); Properties prop=new Properties(); prop.load(is); String username=prop.getProperty("username"); String pwd=prop.getProperty("pwd"); resp.getWriter().print(username+":"+pwd); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }

此外需要注意的是以上的servlet都需要在web.xml中进行配置

<?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" metadata-complete="true"> <context-param> <param-name>url</param-name> <param-value>jdbc:mysql://localhost:3306/myhabits</param-value> </context-param> <servlet> <servlet-name>helloworld</servlet-name> <servlet-class>com.csn.servelet.helloworld</servlet-class> </servlet> <servlet-mapping> <servlet-name>helloworld</servlet-name> <url-pattern>/hellocsn</url-pattern> </servlet-mapping> <servlet> <servlet-name>servletcontext</servlet-name> <servlet-class>com.csn.servelet.servletContext</servlet-class> </servlet> <servlet-mapping> <servlet-name>servletcontext</servlet-name> <url-pattern>/servletcontext</url-pattern> </servlet-mapping> <servlet> <servlet-name>servledemp03</servlet-name> <servlet-class>com.csn.servelet.servletDemo03</servlet-class> </servlet> <servlet-mapping> <servlet-name>servledemp03</servlet-name> <url-pattern>/servledemp03</url-pattern> </servlet-mapping> <servlet> <servlet-name>servledemp041</servlet-name> <servlet-class>com.csn.servelet.servletDemo04_1</servlet-class> </servlet> <servlet-mapping> <servlet-name>servledemp041</servlet-name> <url-pattern>/Startservledemp04</url-pattern> </servlet-mapping> <servlet> <servlet-name>servledemp04</servlet-name> <servlet-class>com.csn.servelet.servletDemo04</servlet-class> </servlet> <servlet-mapping> <servlet-name>servledemp04</servlet-name> <url-pattern>/Runservledemp04</url-pattern> </servlet-mapping> <servlet> <servlet-name>servledemp05</servlet-name> <servlet-class>com.csn.servelet.servletDemo05</servlet-class> </servlet> <servlet-mapping> <servlet-name>servledemp05</servlet-name> <url-pattern>/servledemp05</url-pattern> </servlet-mapping> <servlet> <servlet-name>servledemp06</servlet-name> <servlet-class>com.csn.servelet.servletDemo06</servlet-class> </servlet> <servlet-mapping> <servlet-name>servledemp06</servlet-name> <url-pattern>/servledemp06</url-pattern> </servlet-mapping> </web-app>

8.Response

重定向：url会发生改变

转发：url不会发生改变

9.HttpServletRequest

将前端请求的信息都封装到这个类里面，通过调用类来获得信息

10.Cookie

11.Session

12.JSP

错误页面设置

<error-page> <error-code>500</error-code> <location>/common/error.jsp</location> </error-page>

导入别的页面

<html> <body> <h2>Hello World!</h2> <%@include file="common/header.jsp"%> <jsp:include page="/common/header.jsp"/>/*建议使用*/ </body> </html>

13.JSTL

14.JavaBean

必须有无参构造

属性必须私有化

必须有对应的get/set方法

一般用来的和数据库的字段做映射ORM

ORM对象关系映射

表对应类

字段对应属性

表记录对应对象

15.三层架构MVC

Model：

业务处理：业务层

数据持久层CURD

View

展示数据

提供发起servlet请求

Controller

接受用户请求

交给业务层处理对应代码

控制视图跳转

早期：

用户直接访问控制器，控制器直接访问数据库

架构：没有什么是加一层是解决不了的

MVC

16.Fliter

过滤器：过滤网站的数据：

解决乱码登陆验证

其实和servlet一样

1.导包不要导错

package com.csn.Fliter; import javax.servlet.*; import java.io.IOException; public class EncodingFliter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { } @Override public void destroy() { } }

2.编辑过滤层

package com.csn.Fliter; import javax.servlet.*; import java.io.IOException; public class EncodingFliter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { System.out.println("EncodingFliter启动"); } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { response.setCharacterEncoding("utf-8"); request.setCharacterEncoding("utf-8"); chain.doFilter(request,response);//必须得要加的东西 } @Override public void destroy() { System.out.println("EncodingFliter关闭"); } }

3.设置mapping

<servlet> <servlet-name>testFilter</servlet-name> <servlet-class>com.csn.servelet.TestFilter</servlet-class> </servlet> <servlet-mapping> <servlet-name>testFilter</servlet-name> <url-pattern>/show</url-pattern> </servlet-mapping> <servlet> <servlet-name>testFilter2</servlet-name> <servlet-class>com.csn.servelet.TestFilter</servlet-class> </servlet> <servlet-mapping> <servlet-name>testFilter2</servlet-name> <url-pattern>/Filter/show</url-pattern> </servlet-mapping> <filter> <filter-name>filter</filter-name> <filter-class>com.csn.Fliter.EncodingFliter</filter-class> </filter> <filter-mapping> <filter-name>filter</filter-name> <url-pattern>/Filter/*</url-pattern> </filter-mapping>

17.基于Filter的权限管理

1.用户登记之后，向session中向放入用户的数据

package com.csn.Fliter; 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 LoginServelt extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String username=req.getParameter("username"); if(username.equals("admin")){ req.getSession().setAttribute("USER_SESSION",req.getSession().getId()); resp.sendRedirect("/sys/success.jsp"); }else { resp.sendRedirect("/error.jsp"); } } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } }

2.利用Filter过滤器实现进主页的时候要判断用户是否已经登陆

package com.csn.Fliter; import javax.servlet.*; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class sysFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException { HttpServletRequest request=(HttpServletRequest)req; HttpServletResponse response=(HttpServletResponse)resp; if(request.getSession().getAttribute("USER_SESSION")==null){ response.sendRedirect("/error.jsp"); } chain.doFilter(request,response); } @Override public void destroy() { } }

配置mapping

<filter> <filter-name>sysfilter</filter-name> <filter-class>com.csn.Fliter.sysFilter</filter-class> </filter> <filter-mapping> <filter-name>sysfilter</filter-name> <url-pattern>/sys/*</url-pattern> </filter-mapping>

18.JDBC

1.加载驱动

2.连接数据库

3.向数据库发送SQL的对象statement：CURD

4.编写sql语言

5.执行SQL语言

6.关闭连接

开启事务：

connection.setAutoCommit（false）

很重要！！！

19.单元测试

配置

<dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> </dependency>

使用

package com.csn.jdbc; import org.junit.Test; public class test { @Test public void test(){ System.out.println("hello"); } }

est,response); }

@Override public void destroy() { }

}

配置mapping ```java <filter> <filter-name>sysfilter</filter-name> <filter-class>com.csn.Fliter.sysFilter</filter-class> </filter> <filter-mapping> <filter-name>sysfilter</filter-name> <url-pattern>/sys/*</url-pattern> </filter-mapping>