【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>