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：
1 <modules>
2 <module>demo-project-web</module>
3 <module>demo-project-gods-web</module>
4 <module>demo-project-customer-web</module>
5 <module>demo-project-gods-core</module>
6 <module>demo-common</module>
7 </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：
1 <?xml version="1.0 "?>
2 <project
3 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd "
4 xmlns="http://maven.apache.org/POM/4.0.0 " xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance
">
5 <modelVersion>4.0.0</modelVersion>
6
7 <parent>
8 <groupId>com.demo</groupId>
9 <artifactId>demo-parent</artifactId>
10 <version>0.0.1-SNAPSHOT</version>
11 </parent>
12
13 <groupId>com.demo</groupId>
14 <artifactId>demo-project-web</artifactId>
15 <version>0.0.1-SNAPSHOT</version>
16 <packaging>war</packaging>
17 <name>demo-project-web Maven Webapp</name>
18 <url>http://maven.apache.org</url>
19
20 <dependencies>
21
22 <!-- 增加要合并的war包依赖 -->
23 <dependency>
24 <groupId>com.demo</groupId>
25 <artifactId>demo-project-gods-web</artifactId>
26 <version>0.0.1-SNAPSHOT</version>
27 <type>war</type>
28 </dependency>
29 <dependency>
30 <groupId>com.demo</groupId>
31 <artifactId>demo-project-customer-web</artifactId>
32 <version>0.0.1-SNAPSHOT</version>
33 <type>war</type>
34 </dependency>
35
36 <dependency>
37 <groupId>junit</groupId>
38 <artifactId>junit</artifactId>
39 <version>3.8.1</version>
40 <scope>test</scope>
41 </dependency>
42
43 </dependencies>
44
45 <build>
46
47 <finalName>demo-project-web</finalName>
48
49 <plugins>
50
51 <plugin>
52 <groupId>org.apache.maven.plugins</groupId>
53 <artifactId>maven-war-plugin</artifactId>
54 <version>2.6</version>
55 <configuration>
56 <!-- 把另外2个web子工程加入进来, 合并war -->
57 <overlays>
58 <overlay>
59 <groupId>com.demo</groupId>
60 <artifactId>demo-project-gods-web</artifactId>
61 </overlay>
62 <overlay>
63 <groupId>com.demo</groupId>
64 <artifactId>demo-project-customer-web</artifactId>
65 </overlay>
66 </overlays>
67 </configuration>
68 </plugin>
69
70 </plugins>
71 </build>
72
73 </project>
修改demo-project-gods-web的pom，添加自身依赖core作为service以及DAO
1 <?xml version="1.0 "?>
2 <project
3 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd "
4 xmlns="http://maven.apache.org/POM/4.0.0 " xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance
">
5 <modelVersion>4.0.0</modelVersion>
6 <parent>
7 <groupId>com.demo</groupId>
8 <artifactId>demo-parent</artifactId>
9 <version>0.0.1-SNAPSHOT</version>
10 </parent>
11 <groupId>com.demo</groupId>
12 <artifactId>demo-project-gods-web</artifactId>
13 <version>0.0.1-SNAPSHOT</version>
14 <packaging>war</packaging>
15 <name>demo-project-gods-web Maven Webapp</name>
16 <url>http://maven.apache.org</url>
17
18 <dependencies>
19
20 <!-- 引入依赖, core中包含service以及DAO -->
21 <dependency>
22 <groupId>com.demo</groupId>
23 <artifactId>demo-project-gods-core</artifactId>
24 <version>0.0.1-SNAPSHOT</version>
25 </dependency>
26
27 <dependency>
28 <groupId>junit</groupId>
29 <artifactId>junit</artifactId>
30 <version>3.8.1</version>
31 <scope>test</scope>
32 </dependency>
33
34 </dependencies>
35
36 <build>
37 <finalName>demo-project-gods-web</finalName>
38 </build>
39 </project>在customer中添加工具类依赖
1 <?xml version="1.0 "?>
2 <project
3 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd "
4 xmlns="http://maven.apache.org/POM/4.0.0 " xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance
">
5 <modelVersion>4.0.0</modelVersion>
6 <parent>
7 <groupId>com.demo</groupId>
8 <artifactId>demo-parent</artifactId>
9 <version>0.0.1-SNAPSHOT</version>
10 </parent>
11 <groupId>com.demo</groupId>
12 <artifactId>demo-project-customer-web</artifactId>
13 <version>0.0.1-SNAPSHOT</version>
14 <packaging>war</packaging>
15 <name>demo-project-customer-web Maven Webapp</name>
16 <url>http://maven.apache.org</url>
17 <dependencies>
18
19 <!-- 添加common工具类依赖 -->
20 <dependency>
21 <groupId>com.demo</groupId>
22 <artifactId>demo-common</artifactId>
23 <version>0.0.1-SNAPSHOT</version>
24 </dependency>
25
26 <dependency>
27 <groupId>junit</groupId>
28 <artifactId>junit</artifactId>
29 <version>3.8.1</version>
30 <scope>test</scope>
31 </dependency>
32
33 </dependencies>
34 <build>
35 <finalName>demo-project-customer-web</finalName>
36 </build>
37 </project>
============进入代码阶段============
parent是父工程，不需要编写代码
demo-common：
1 package org.demo.common;
2
3 import java.util.Date;
4
5 public class DateUtil {
6
7 public static void showTime(String name) {
8 System.out.println("Run in demo-common - Hello ~ " + name + ", it is " + new Date().toString());
9 }
10
11 }demo-project-customer-web：
1 package com.demo.project.customer.web;
2
3 import org.demo.common.DateUtil;
4
5 public class AbcService {
6
7 public static void getDateService(String name) {
8 DateUtil.showTime(name);
9 System.out.println("Run in demo-project-customer-web... ");
10 }
11
12 }customer.jsp
1 <?xml version="1.0 " encoding="UTF-8 " ?>
2 <%@page import="com.demo.project.customer.web.AbcService"
%> 3 <%@ page language
="java"
contentType="text/html; charset=UTF-8
" 4 pageEncoding=
"UTF-8"%> 5 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"
> 6 <html xmlns
="http://www.w3.org/1999/xhtml" 7 xmlns:f="http://java.sun.com/jsf/core" 8 xmlns:h="http://java.sun.com/jsf/html"> 9 <head> 10 <meta http-equiv="Content-Type"
content="text/html; charset=UTF-8" /> 11 <
title>Insert title here</title> 12 </head> 13 <body> 14 <% 15 System.out.print(
"hello demo-project-customer-web customer.jsp"
); 16 AbcService.getDateService("
abc");
17 %> 18 19 </body
> 20 </html>
demo-project-gods-core：
1 package org.demo.project.gods.core;
2
3
4 public class Gods {
5
6 public static void getDateService(String name) {
7 System.out.println("Run in demo-project-gods-core...");
8 }
9
10 }demo-project-gods-web
index.jsp
1 <?xml version="1.0" encoding="UTF-8" ?>
2 <%@page import="org.demo.project.gods.core.Gods"%>
3 <%@ page language="java" contentType="text/html; charset=UTF-8"
4 pageEncoding="UTF-8"%>
5 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
6 <html xmlns="http://www.w3.org/1999/xhtml"
7 xmlns:f="http://java.sun.com/jsf/core"
8 xmlns:h="http://java.sun.com/jsf/html">
9 <head>
10 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
11 <title>Insert title here</title>
12 </head>
13 <body>
14
15 <%
16 System.out.print("hello demo-project-gods-web gods.jsp");
17 Gods.getDateService("nathan");
18
19 %>
20 </body>
21 </html>
run - mvn install:
运行成功，进入相应的页面则成功
