【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>