maven 多工程搭建演示

maven出现后，很多公司会用maven来构建项目，单仅仅只是单项目单工程的

并没有使用多工程来构建，这样在以后，项目越来越大，业务越来越多以后，项目会难以维护，越发庞大，维护成本提高，团队士气也会下降

等等情况，使用maven构建多工程就是如今的趋势

这边演示一个maven工程相互依赖的例子，高手轻拍，大家互相学习，有不足之处请指出

1.新建demo-parent项目，作为父工程

选择quickstart

修改pom中的jar改为pom，这样的意思是当前工程为父工程，可以再其下创建子工程

2.新建demo-project-web，作为web工程，这个工程是总的web工程，下面将会包含另外2个子web工程

选择webapp作为web工程

3.同理创建demo-project-customer-web作为子web工程（webapp），这个工程是一个独立web工程，他包含了service，dao

4.同理创建demo-project-gods-web作为子web工程（webapp），这个工程将有一个demo-project-gods-core作为后台（core就是包含了service，dao）

5.创建demo-project-gods-core作为子工程（quickstart），依赖demo-project-gods-web

6.创建demo-common，作为子工程（quickstart），作用是工具包，可被其他工程依赖引用

3-6步骤略，生成项目如下图：

父工程pom会成这样：

 <modules>
       <module>demo-project-web</module>
       <module>demo-project-gods-web</module>
       <module>demo-project-customer-web</module>
       <module>demo-project-gods-core</module>
       <module>demo-common</module>
   </modules>

好，那么现在来做工程之间的依赖

首先，demo-project-web作为顶级web项目，所有的子web项目打包后都会整合在此（如果同名文件则被顶级覆盖，如果顶级没有同名文件，但是子web有同名文件，则按照依赖顺序被优先依赖的同名文件覆盖）

pom如下：

 <?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.demo</groupId>
         <artifactId>demo-parent</artifactId>
         <version>0.0.1-SNAPSHOT</version>
     </parent>

     <groupId>com.demo</groupId>
     <artifactId>demo-project-web</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <packaging>war</packaging>
     <name>demo-project-web Maven Webapp</name>
     <url>http://maven.apache.org</url>

     <dependencies>

         <!-- 增加要合并的war包依赖 -->
         <dependency>
             <groupId>com.demo</groupId>
             <artifactId>demo-project-gods-web</artifactId>
             <version>0.0.1-SNAPSHOT</version>
             <type>war</type>
         </dependency>
         <dependency>
             <groupId>com.demo</groupId>
             <artifactId>demo-project-customer-web</artifactId>
             <version>0.0.1-SNAPSHOT</version>
             <type>war</type>
         </dependency>

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

     </dependencies>

     <build>

         <finalName>demo-project-web</finalName>

         <plugins>

             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-war-plugin</artifactId>
                 <version>2.6</version>
                 <configuration>
                     <!-- 把另外2个web子工程加入进来, 合并war -->
                     <overlays>
                         <overlay>
                             <groupId>com.demo</groupId>
                             <artifactId>demo-project-gods-web</artifactId>
                         </overlay>
                         <overlay>
                             <groupId>com.demo</groupId>
                             <artifactId>demo-project-customer-web</artifactId>
                         </overlay>
                     </overlays>
                 </configuration>
             </plugin>

         </plugins>
     </build>

 </project>

修改demo-project-gods-web的pom，添加自身依赖core作为service以及DAO

 <?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.demo</groupId>
         <artifactId>demo-parent</artifactId>
         <version>0.0.1-SNAPSHOT</version>
     </parent>
     <groupId>com.demo</groupId>
     <artifactId>demo-project-gods-web</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <packaging>war</packaging>
     <name>demo-project-gods-web Maven Webapp</name>
     <url>http://maven.apache.org</url>

     <dependencies>

         <!-- 引入依赖, core中包含service以及DAO -->
         <dependency>
             <groupId>com.demo</groupId>
             <artifactId>demo-project-gods-core</artifactId>
             <version>0.0.1-SNAPSHOT</version>
         </dependency>

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

     </dependencies>

     <build>
         <finalName>demo-project-gods-web</finalName>
     </build>
 </project>

在customer中添加工具类依赖

 <?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.demo</groupId>
         <artifactId>demo-parent</artifactId>
         <version>0.0.1-SNAPSHOT</version>
     </parent>
     <groupId>com.demo</groupId>
     <artifactId>demo-project-customer-web</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <packaging>war</packaging>
     <name>demo-project-customer-web Maven Webapp</name>
     <url>http://maven.apache.org</url>
     <dependencies>

         <!-- 添加common工具类依赖 -->
         <dependency>
             <groupId>com.demo</groupId>
             <artifactId>demo-common</artifactId>
             <version>0.0.1-SNAPSHOT</version>
         </dependency>

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

     </dependencies>
     <build>
         <finalName>demo-project-customer-web</finalName>
     </build>
 </project>

============进入代码阶段============

parent是父工程，不需要编写代码

demo-common：

 package org.demo.common;

 import java.util.Date;

 public class DateUtil {

     public static void showTime(String name) {
         System.out.println("Run in demo-common - Hello ~ " + name + ", it is " + new Date().toString());
     }

 }

demo-project-customer-web：

 package com.demo.project.customer.web;

 import org.demo.common.DateUtil;

 public class AbcService {

     public static void getDateService(String name) {
         DateUtil.showTime(name);
         System.out.println("Run in demo-project-customer-web...");
     }

 }

customer.jsp

 <?xml version="1.0" encoding="UTF-8" ?>
 <%@page import="com.demo.project.customer.web.AbcService"%>
 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml"
     xmlns:f="http://java.sun.com/jsf/core"
     xmlns:h="http://java.sun.com/jsf/html">
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
 <title>Insert title here</title>
 </head>
 <body>
     <%
         System.out.print("hello demo-project-customer-web customer.jsp");
         AbcService.getDateService("abc");
     %>

 </body>
 </html>

demo-project-gods-core：

 package org.demo.project.gods.core;

 public class Gods {

     public static void getDateService(String name) {
         System.out.println("Run in demo-project-gods-core...");
     }

 }

demo-project-gods-web

index.jsp

 <?xml version="1.0" encoding="UTF-8" ?>
 <%@page import="org.demo.project.gods.core.Gods"%>
 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml"
     xmlns:f="http://java.sun.com/jsf/core"
     xmlns:h="http://java.sun.com/jsf/html">
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
 <title>Insert title here</title>
 </head>
 <body>

     <%
         System.out.print("hello demo-project-gods-web gods.jsp");
         Gods.getDateService("nathan");

     %>
 </body>
 </html>

run - mvn install:

运行成功，进入相应的页面则成功