Mybatis Generator使用自定义Generator Plugin

使用Mybatis Generator Plugin自动生成Mapper、Model和相关配置文件。但是在实际使用情况中，可能会遇到不同的个性化需求，那么就需要Generator的自定义插件来实现。

1、创建基类

在项目中，我们经常要把一些具有通用方法的实体类建立一个基类，提高代码复用程度。 
假设每一个表中都有字段id和username，且每一个表都需要类似的CRUD方法（如根据主键查XX等）。

public class BaseModel {
    private Integer id;
    private String username;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }
}

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public interface BaseMapper<T extends BaseModel> {

    List<T> selectAll();

    int deleteByPrimaryKey(Integer id);

    int insert(T record);

    int insertSelective(T record);

    T selectByPrimaryKey(Integer id);

    int updateByPrimaryKey(T record);
}

• 2、修改generatorConfig.xml

加入插件标签

<!-- 自动生成toString方法 -->
        <plugin type="org.mybatis.generator.plugins.ToStringPlugin"/>
        <!-- 自动生成equals方法和hashcode方法 -->
        <plugin type="org.mybatis.generator.plugins.EqualsHashCodePlugin"/>
        <!-- 自定义方法 -->
        <plugin type="com.dfz.plugin.MapperPlugin">
            <property name="targetProject" value="../Mybatis-Chapter9-GeneratorPlugin/src/main/java"/>
            <property name="targetPackage" value="com.dfz.mybatis.dao"/>
        </plugin>
        <!-- 自定义方法 -->
        <plugin type="com.dfz.plugin.SerializablePlugin"/>

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并给model和dao添加基类属性

<javaModelGenerator targetPackage="com.dfz.mybatis.model" targetProject="src/main/java">
            <property name="enableSubPackages" value="true" />
            <property name="trimStrings" value="true" />
            <property name="rootClass" value="com.dfz.base.BaseModel"/>
        </javaModelGenerator>

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<javaClientGenerator type="XMLMAPPER" targetPackage="com.dfz.mybatis.dao"  targetProject="src/main/java">
            <property name="enableSubPackages" value="true" />
            <property name="rootInterface" value="com.dfz.base.BaseMapper"/>
        </javaClientGenerator>

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3、创建MapperPlugin

编写自己的Plugin

public class MapperPlugin extends PluginAdapter {

    private static final String DEFAULT_DAO_SUPER_CLASS = "com.dfz.base.BaseMapper";
    private static final String DEFAULT_EXPAND_DAO_SUPER_CLASS = "com.dfz.base.BaseExpandMapper";
    private String daoTargetDir;
    private String daoTargetPackage;

    private String daoSuperClass;

    // 扩展
    private String expandDaoTargetPackage;
    private String expandDaoSuperClass;

    private ShellCallback shellCallback = null;

    public MapperPlugin() {
        shellCallback = new DefaultShellCallback(false);
    }

    /**
     * 验证参数是否有效
     * @param warnings
     * @return
     */
    public boolean validate(List<String> warnings) {
        daoTargetDir = properties.getProperty("targetProject");
        boolean valid = stringHasValue(daoTargetDir);

        daoTargetPackage = properties.getProperty("targetPackage");
        boolean valid2 = stringHasValue(daoTargetPackage);

        daoSuperClass = properties.getProperty("daoSuperClass");
        if (!stringHasValue(daoSuperClass)) {
            daoSuperClass = DEFAULT_DAO_SUPER_CLASS;
        }

        expandDaoTargetPackage = properties.getProperty("expandTargetPackage");
        expandDaoSuperClass = properties.getProperty("expandDaoSuperClass");
        if (!stringHasValue(expandDaoSuperClass)) {
            expandDaoSuperClass = DEFAULT_EXPAND_DAO_SUPER_CLASS;
        }
        return valid && valid2;
    }

    @Override
    public boolean sqlMapDocumentGenerated(Document document, IntrospectedTable introspectedTable) {
        XmlElement select = new XmlElement("select");
        select.addAttribute(new Attribute("id", "selectAll"));
        select.addAttribute(new Attribute("resultMap", "BaseResultMap"));
        select.addAttribute(new Attribute("parameterType", introspectedTable.getBaseRecordType()));
        select.addElement(new TextElement(" select * from "+ introspectedTable.getFullyQualifiedTableNameAtRuntime()));

        XmlElement parentElement = document.getRootElement();
        parentElement.addElement(select);
        return super.sqlMapDocumentGenerated(document, introspectedTable);
    }

    public List<GeneratedJavaFile> contextGenerateAdditionalJavaFiles(IntrospectedTable introspectedTable) {
        JavaFormatter javaFormatter = context.getJavaFormatter();
        List<GeneratedJavaFile> mapperJavaFiles = new ArrayList<GeneratedJavaFile>();
        for (GeneratedJavaFile javaFile : introspectedTable.getGeneratedJavaFiles()) {
            CompilationUnit unit = javaFile.getCompilationUnit();
            FullyQualifiedJavaType baseModelJavaType = unit.getType();

            String shortName = baseModelJavaType.getShortName();

            GeneratedJavaFile mapperJavafile = null;

            if (shortName.endsWith("Mapper")) { // 扩展Mapper
                if (stringHasValue(expandDaoTargetPackage)) {
                    Interface mapperInterface = new Interface(
                            expandDaoTargetPackage + "." + shortName.replace("Mapper", "ExpandMapper"));
                    mapperInterface.setVisibility(JavaVisibility.PUBLIC);
                    mapperInterface.addJavaDocLine("/**");
                    mapperInterface.addJavaDocLine(" * " + shortName + "扩展");
                    mapperInterface.addJavaDocLine(" */");

                    FullyQualifiedJavaType daoSuperType = new FullyQualifiedJavaType(expandDaoSuperClass);
                    mapperInterface.addImportedType(daoSuperType);
                    mapperInterface.addSuperInterface(daoSuperType);

                    mapperJavafile = new GeneratedJavaFile(mapperInterface, daoTargetDir, javaFormatter);
                    try {
                        File mapperDir = shellCallback.getDirectory(daoTargetDir, daoTargetPackage);
                        File mapperFile = new File(mapperDir, mapperJavafile.getFileName());
                        // 文件不存在
                        if (!mapperFile.exists()) {
                            mapperJavaFiles.add(mapperJavafile);
                        }
                    } catch (ShellException e) {
                        e.printStackTrace();
                    }
                }
            } else if (!shortName.endsWith("Example")) { // CRUD Mapper
                Interface mapperInterface = new Interface(daoTargetPackage + "." + shortName + "Mapper");

                mapperInterface.setVisibility(JavaVisibility.PUBLIC);
                mapperInterface.addJavaDocLine("/**");
                mapperInterface.addJavaDocLine(" * 由MyBatis Generator工具自动生成，请不要手动修改");
                mapperInterface.addJavaDocLine(" */");

                FullyQualifiedJavaType daoSuperType = new FullyQualifiedJavaType(daoSuperClass);
                // 添加泛型支持
                daoSuperType.addTypeArgument(baseModelJavaType);
                mapperInterface.addImportedType(baseModelJavaType);
                mapperInterface.addImportedType(daoSuperType);
                mapperInterface.addSuperInterface(daoSuperType);

                mapperJavafile = new GeneratedJavaFile(mapperInterface, daoTargetDir, javaFormatter);
                mapperJavaFiles.add(mapperJavafile);

            }
        }
        return mapperJavaFiles;
    }
}

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4、注意事项

1）在添加完成自定义的plugin标签后，直接mvn:mybatis-generator:generate会报classNotFound错误，这是因为maven找不到相应的包导致的。有两种解决方案： 
a）首先使用maven打包项目mvn:install，然后再把打包好的项目添加到插件的依赖中：

<plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.2</version>
                <configuration>
                    <verbose>true</verbose>
                    <overwrite>true</overwrite>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>com.dfz</groupId>
                        <artifactId>Mybatis-Chapter9-GeneratorPlugin</artifactId>
                        <version>1.0-SNAPSHOT</version>
                    </dependency>
                </dependencies>
            </plugin>

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当然这是比较坑爹的办法，不仅很慢而且无法调试。 
b）创建一个新的类，按照mybatis-generator官方所给出的方法，代码如下：

public class TestGenerator {

    private File configFile;

    @Before
    public void before() {
        //读取mybatis参数
        configFile = new File("/Users/Documents/MybatisFun/Mybatis-Chapter9-GeneratorPlugin/src/main/resources/generatorConfig.xml");

//        configFile = new File("/Users/zhangsiyuan/Documents/MybatisFun/Mybatis-Chapter9-GeneratorPlugin/src/main/resources/mybatisConfig.xml");
    }

    @Test
    public void test() throws Exception{
        List<String> warnings = new ArrayList<String>();
        boolean overwrite = true;
        ConfigurationParser cp = new ConfigurationParser(warnings);
        Configuration config = cp.parseConfiguration(configFile);
        DefaultShellCallback callback = new DefaultShellCallback(overwrite);
        MyBatisGenerator myBatisGenerator = new MyBatisGenerator(config, callback, warnings);
        myBatisGenerator.generate(null);
    }
}

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直接运行就可以生成代码了。 
2）plugin里头的方法挺多的，大多数用反射和动态代理实现的，需要好好看一下，以后用得到的时候再来。