Java WEB框架——SSM之Hello world

一、建立项目

先搭建一个webapp项目(要选creat from arctype)

起名

选择maven路径，settings.xml那里要选择override才可以在资源管理器中浏览。接下来直接Next直到Finish。

二、构建文件目录

main下面新建java文件夹，并且标记为sources root

然后同样的操作把resource文件夹变成resources root

打开project structure找到Modules，如下图所示，如果没有Web，那就点击左上角的加号添加，然后把下面红圈处的路径改为你webapp的路径。

然后就会变成下面这样，src下面的三个文件夹各有自己的特色。

java下面放java文件，建立该建立的package；webapp下面有一个WEB-INF文件夹，首先要有一个web.xml；项目根目录和src文件夹下还有pom.xml和.idea文件夹以及SSM.iml

三、代码

POM.XML

先打开pom.xml，pom全程Project Object Model，是maven的文件。maven的世界里必须要有pom文件。

该文件用于管理：源代码、配置文件、开发者的信息和角色、问题追踪系统、组织信息、项目授权、项目的url、项目的依赖关系等等。(来源)

<?xml version="1.0" encoding="UTF-8"?>
<!--
  Licensed to the Apache Software Foundation (ASF) under one
  or more contributor license agreements.  See the NOTICE file
  distributed with this work for additional information
  regarding copyright ownership.  The ASF licenses this file
  to you under the Apache License, Version 2.0 (the
  "License"); you may not use this file except in compliance
  with the License.  You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing,
  software distributed under the License is distributed on an
  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  KIND, either express or implied.  See the License for the
  specific language governing permissions and limitations
  under the License.
-->
<!-- $Id: pom.xml 642118 2008-03-28 08:04:16Z reinhard $ -->
<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/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>
  <packaging>war</packaging>

  <name>SSM</name>
  <groupId>com.demo</groupId>
  <artifactId>SSM</artifactId>
  <version>1.0-SNAPSHOT</version>

  <build>
    <plugins>
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>maven-jetty-plugin</artifactId>
        <version>6.1.7</version>
        <configuration>
          <connectors>
            <connector implementation="org.mortbay.jetty.nio.SelectChannelConnector">
              <port>8888</port>
              <maxIdleTime>30000</maxIdleTime>
            </connector>
          </connectors>
          <webAppSourceDirectory>${project.build.directory}/${pom.artifactId}-${pom.version}</webAppSourceDirectory>
          <contextPath>/</contextPath>
        </configuration>
      </plugin>
    </plugins>
  </build>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>

    <!-- Servlet Library -->
    <!-- http://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>

    <!-- Spring dependencies -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>4.1.4.RELEASE</version>
    </dependency>

    <!-- http://mvnrepository.com/artifact/org.springframework/spring-web -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>4.1.4.RELEASE</version>
    </dependency>

    <!-- http://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>4.1.4.RELEASE</version>
    </dependency>
  </dependencies>

</project>

我坦白，pom文件是抄别人的，毕竟我只是一个刚开始学习新手，不先抄无从下手啊。抄完发现全是错误，各种can not resolve

此时IDEA会提示maven project need to be imported，表示你修改了pom文件，此时需要同步下载相应的jar包，这时出现两个选项，一个是imported changes，还有一个是Enable auto-import。 后者会自动更新，前者手动更新，不过应该都没太差，选择之后都会进行同步，同步后大部分错误会消失。

WEB.XML

<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/javaeehttp://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
         id="WebApp_ID" version="3.0">
  <display-name>HelloWorldSpring</display-name>

  <servlet>
    <servlet-name>spring-mvc</servlet-name>
    <servlet-class>
      org.springframework.web.servlet.DispatcherServlet
    </servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>spring-mvc</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

  <!-- Other XML Configuration -->
  <!-- Load by Spring ContextLoaderListener -->

  <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value> /WEB-INF/root-context.xml</param-value>
  </context-param>

  <!-- Spring ContextLoaderListener -->
  <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>

</web-app>

web.xml是具有固定一些标签，例如context-param、listener、servlet等， Tomcat启动之后会加载web.xml，servlet-name代表名称，url-pattern表示何种url被访问时触发该servlet。而DispatcherServlet则会在/WEB-INF文件夹下搜寻{servlet-name}-servlet.xml的文件，即spring-mvc-servlet.xml。

spring-mvc-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
  http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
  http://www.springframework.org/schema/context
  http://www.springframework.org/schema/context/spring-context-4.1.xsd
  http://www.springframework.org/schema/mvc
  http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd">

    <context:component-scan base-package="com.demo.controller"/>

    <context:annotation-config/>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix">
            <value>/WEB-INF/jsp/</value>
        </property>

        <property name="suffix">
            <value>.jsp</value>
        </property>
    </bean>

</beans>

该文件会通过base-package生命作用范围，InternalResourceViewResolver类会将该包下面的类中@RequestMapping获得的字符串作为视图的名称。

HelloworldController.java

package com.demo.controller;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HelloWorldController {
    @RequestMapping("/hello")
    public String hello(Model model){
        model.addAttribute("print","Hello world");
        return "helloworld";
    }
}

前缀/WEB-INF/jsp+字符串helloworld+后缀.jsp 组成路径：/WEB-INF/jsp/helloworld.jsp

正是这个文件：

helloworld.jsp

<%--
  Created by IntelliJ IDEA.
  User: wym
  Date: 2019/10/3
  Time: 21:42
  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>
<h1>${print}</h1>

</body>
</html>

三、运行

添加Artifacts-war

配置默认路径

运行，

阶段性成功吧，但是完全没有使用数据库，因此算不上SSM，最多是maven+springMVC的简单demo.

四、总结

参照https://www.cnblogs.com/fht-litost/p/9873936.html