【Maven】Maven Plugin示例：自己动手编写Maven插件
需求：
在Maven编译项目的时候，统计代码量，即项目中的文件数目、代码行数，包括java文件和配置文件两种；其中配置文件（sql、xml、properties）代码行数/4 处理。
创建项目：
首先确保已安装m2eclipse插件：http://eclipse.org/m2e/
eclipse - new - Maven Project，选择archetype = maven-archetype-plugin：（或用命令 mvn archetype:generate，再按提示操作）
下一步设置好坐标信息，即可创建一个maven plugin工程。
生成的pom.xml文件如下（有手工改动，参见注释）：
<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>com.alpha.wang</groupId>
<artifactId>maven-statis-plugin</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>maven-plugin</packaging>
<name>alpha-statis-plugin Maven Plugin</name>
<url>http://blog.csdn.net/vking_wang</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.apache.maven</groupId>
<artifactId>maven-plugin-api</artifactId>
<version>2.0</version>
</dependency>
<!-- 否则Mojo中的org.apache.maven.model.Resource，无法解析 -->
<dependency>
<groupId>org.apache.maven</groupId>
<artifactId>maven-model</artifactId>
<version>2.2.1</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-plugin-plugin</artifactId>
<version>2.5.1</version>
<configuration>
<!--[WARNING]Goal prefix is specified as: 'maven-statis-plugin'. Maven currently expects it to be 'statis'.-->
<!-- goalPrefix>maven-statis-plugin</goalPrefix-->
<goalPrefix>statis</goalPrefix>
</configuration>
<executions>
<execution>
<id>generated-helpmojo</id>
<goals>
<goal>helpmojo</goal>
</goals>
</execution>
</executions>
</plugin>
<!-- generics are not supported in -source 1.3 (use -source 5 or higher to enable generics)-->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.5.1</version>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
注意packing为maven-plugin；并有对maven-plugin-api的依赖。
还会自动生成一个public class MyMojo extends AbstractMojo的源文件。
编写Mojo
Mojo = Maven Old Java Object，需要继承AbstractMojo，并实现其execute方法。
上一步已经自动生成了一个Mojo，我们删掉重新创建一个：
import org.apache.maven.model.Resource;
import org.apache.maven.plugin.AbstractMojo;
import org.apache.maven.plugin.MojoExecutionException;
/**
*
* @goal count
*
* @phase process-sources
*/
public class CountMojo extends AbstractMojo
{
private static final String[] INCLUDES_DEFAULT = {"java", "xml", "sql", "properties"};
private static final String[] RATIOS_DEFAULT = {"1.0", "0.25", "0.25", "0.25"};
private static final String DOT = ".";
/**
* @parameter expression="${project.basedir}"
* @required
* @readonly
*/
private File basedir;
/**
* @parameter expression="${project.build.sourceDirectory}"
* @required
* @readonly
*/
private File sourcedir;
/**
* @parameter expression="${project.build.testSourceDirectory}"
* @required
* @readonly
*/
private File testSourcedir;
/**
* @parameter expression="${project.resources}"
* @required
* @readonly
*/
private List<Resource> resources;
//private List<File> resources;
/**
* @parameter expression="${project.testResources}"
* @required
* @readonly
*/
private List<Resource> testResources;
//private List<File> testResources;
/**
* @parameter
*/
private String[] includes;
/**
* @parameter
*/
private String[] ratios;//TODO 定义为double[],从xml读取时提示java.lang.ClassCastException: [D cannot be cast to [Ljava.lang.Object;
private Map<String, Double> ratioMap = new HashMap<String, Double>();
private long realTotal;
private long fakeTotal;
public void execute() throws MojoExecutionException
{
initRatioMap();
try{
countDir(sourcedir);
countDir(testSourcedir);
for(Resource res : resources){
countDir(new File(res.getDirectory()));
}
for(Resource res : testResources){
countDir(new File(res.getDirectory()));
}
getLog().info("TOTAL LINES:"+fakeTotal+ " ("+realTotal+")");
}catch (IOException e){
throw new MojoExecutionException("Unable to count lines of code", e);
}
}
}
所调用的工具方法定义如下：
private void initRatioMap() throws MojoExecutionException{
if(includes == null || includes.length == 0){
includes = INCLUDES_DEFAULT;
ratios = RATIOS_DEFAULT;
}
if(ratios == null || ratios.length == 0){
ratios = new String[includes.length];
for(int i=0; i<includes.length; i++){
ratios[i] = "1.0";
}
}
if(includes.length != ratios.length){
throw new MojoExecutionException("pom.xml error: the length of includes is inconsistent with ratios!");
}
ratioMap.clear();
for(int i=0; i<includes.length; i++){
ratioMap.put(includes[i].toLowerCase(), Double.parseDouble(ratios[i]));
}
}
private void countDir(File dir) throws IOException {
if(! dir.exists()){
return;
}
List<File> collected = new ArrayList<File>();
collectFiles(collected, dir);
int realLine = 0;
int fakeLine = 0;
for(File file : collected){
int[] line = countLine(file);
realLine += line[0];
fakeLine += line[1];
}
String path = dir.getAbsolutePath().substring(basedir.getAbsolutePath().length());
StringBuilder info = new StringBuilder().append(path).append(" : ").append(fakeLine).append(" ("+realLine+")")
.append(" lines of code in ").append(collected.size()).append(" files");
getLog().info(info.toString());
}
private void collectFiles(List<File> collected, File file)
throws IOException{
if(file.isFile()){
if(isFileTypeInclude(file)){
collected.add(file);
}
}else{
for(File files : file.listFiles()){
collectFiles(collected, files);
}
}
}
private int[] countLine(File file)
throws IOException{
BufferedReader reader = new BufferedReader(new FileReader(file));
int realLine = 0;
try{
while(reader.ready()){
reader.readLine();
realLine ++;
}
}finally{
reader.close();
}
int fakeLine = (int) (realLine * getRatio(file));
realTotal += realLine;
fakeTotal += fakeLine;
StringBuilder info = new StringBuilder().append(file.getName()).append(" : ").append(fakeLine).append(" ("+realLine+")")
.append(" lines");
getLog().debug(info.toString());
return new int[]{realLine, fakeLine};
}
private double getRatio(File file){
double ratio = 1.0;
String type = getFileType(file);
if(ratioMap.containsKey(type)){
ratio = ratioMap.get(type);
}
return ratio;
}
private boolean isFileTypeInclude(File file){
boolean result = false;
String fileType = getFileType(file);
if(fileType != null && ratioMap.keySet().contains(fileType.toLowerCase())){
result = true;
}
return result;
}
private String getFileType(File file){
String result = null;
String fname = file.getName();
int index = fname.lastIndexOf(DOT);
if(index > 0){
String type = fname.substring(index+1);
result = type.toLowerCase();
}
return result;
}
注意此处 annotation的使用，例如@parameter expression="${project.build.sourceDirectory}"就会自动将项目源代码路径赋值给sourcedir变量。
特别注意@goal，每个插件可有多个目标，在用mvn命令时需要用到这个goal。
执行
可使用mvn clean install将自定义的这个插件安装到本地仓库。
mvn clean install然后在需要统计的项目目录下，调用如下命令即可统计代码行：
mvn com.alpha.wang:maven-statis-plugin:0.0.1-SNAPSHOT:count最后一个冒号后面，就是上面定义的@goal。
显然这个命令太长了，使用很不方便，可在settings.xml中配置如下：
<pluginGroups> <pluginGroup>com.alpha.wang</pluginGroup> </pluginGroups>这样上述命令可以简写为：
mvn statis:count
提供配置点
Mojo的includes、ratios变量标记为@parameter，表示用户可在pom.xml中配置该字段；例如可在目标项目的pom.xml中增加如下内容：
<build> <plugins> <plugin> <groupId>com.alpha.wang</groupId> <artifactId>maven-statis-plugin</artifactId> <version>0.0.1-SNAPSHOT</version> <configuration> <includes> <!--include>java</include--> <include>properties</include> </includes> <ratios> <ratio>1.5</ratio> </ratios> </configuration> </plugin>再在该项目上运行mvn statis:count时就只会统计properties文件了，并将代码量*1.5。
D:\>mvn statis:count
[INFO] Scanning for projects...
[INFO] Searching repository for plugin with prefix: 'statis'.
[INFO] ------------------------------------------------------------------------
[INFO] Building com.。。。
[INFO] task-segment: [statis:count]
[INFO] ------------------------------------------------------------------------
[INFO] [statis:count]
[INFO] \src\main\java : 0 (0) lines of code in 0 files
[INFO] \src\main\resources : 18 (12) lines of code in 1 files
[INFO] TOTAL LINES:18 (12)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: < 1 second
[INFO] Finished at: Tue Feb 26 17:11:22 CST 2013
[INFO] Final Memory: 6M/215M
[INFO] ------------------------------------------------------------------------
绑定插件
那么每次都必须手工执行命令来统计代码量吗？我们可以绑定插件到生命周期的某个阶段，例如install阶段，那么只要每次install该项目的时候，就会自动统计代码量。
修改目标项目的pom文件，注意<phase>、<goals>标签：
<build>
<plugins>
<plugin>
<groupId>com.alpha.wang</groupId>
<artifactId>maven-statis-plugin</artifactId>
<version>0.0.1-SNAPSHOT</version>
<configuration>
<includes>
<include>java</include>
<include>properties</include>
</includes>
<ratios>
<ratio>1.0</ratio>
<ratio>0.5</ratio>
</ratios>
</configuration>
<executions>
<execution>
<id>count line number</id>
<phase>install</phase>
<goals>
<goal>count</goal>
</goals>
</execution>
</executions>
</plugin>