【Maven】Maven Plugin示例：自己動手編寫Maven插件

需求：

在Maven編譯項目的時候，統計代碼量，即項目中的文件數目、代碼行數，包括java文件和配置文件兩種；其中配置文件（sql、xml、properties）代碼行數/4 處理。

創建項目：

首先確保已安裝m2eclipse插件：http://eclipse.org/m2e/

eclipse - new - Maven Project，選擇archetype = maven-archetype-plugin：（或用命令 mvn archetype:generate，再按提示操作）

下一步設置好座標信息，即可創建一個maven plugin工程。

生成的pom.xml文件如下（有手工改動，參見注釋）：

<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>
    <!-- 否則Mojo中的org.apache.maven.model.Resource，無法解析 -->
    <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爲maven-plugin；並有對maven-plugin-api的依賴。

還會自動生成一個public class MyMojo    extends AbstractMojo的源文件。

編寫Mojo

Mojo = Maven Old Java Object，需要繼承AbstractMojo，並實現其execute方法。

上一步已經自動生成了一個Mojo，我們刪掉重新創建一個：

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 定義爲double[],從xml讀取時提示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);
        }

    }
}

所調用的工具方法定義如下：

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;
}

注意此處annotation的使用，例如@parameter expression="${project.build.sourceDirectory}"就會自動將項目源代碼路徑賦值給sourcedir變量。

特別注意@goal，每個插件可有多個目標，在用mvn命令時需要用到這個goal。

執行

可使用mvn clean install將自定義的這個插件安裝到本地倉庫。

mvn clean install

然後在需要統計的項目目錄下，調用如下命令即可統計代碼行：

mvn com.alpha.wang:maven-statis-plugin:0.0.1-SNAPSHOT:count

最後一個冒號後面，就是上面定義的@goal。

顯然這個命令太長了，使用很不方便，可在settings.xml中配置如下：

<pluginGroups>
    <pluginGroup>com.alpha.wang</pluginGroup>
</pluginGroups>

這樣上述命令可以簡寫爲：

mvn statis:count

提供配置點

Mojo的includes、ratios變量標記爲@parameter，表示用戶可在pom.xml中配置該字段；例如可在目標項目的pom.xml中增加如下內容：

<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>

再在該項目上運行mvn statis:count時就只會統計properties文件了，並將代碼量*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] ------------------------------------------------------------------------

綁定插件

那麼每次都必須手工執行命令來統計代碼量嗎？我們可以綁定插件到生命週期的某個階段，例如install階段，那麼只要每次install該項目的時候，就會自動統計代碼量。

修改目標項目的pom文件，注意<phase>、<goals>標籤：

<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>