Mybatis Generator插件 - 实践

关于 mybatis generator 插件，官方提供了一些参考的third-party-tools，但是在实际开发的项目中，遇到了一些相关的问题，以下是写相关记录（主要是配合 gradle 使用）。

1. LombokPlugin 插件

这个很多博客上都有，也就不再重复论了，贴一下 code

public class LombokPlugin extends PluginAdapter {

    private final Set<Annotations> annotations;

    /**
     * LombokPlugin constructor
     */
    public LombokPlugin() {
        annotations = new LinkedHashSet<>(Annotations.values().length);
    }

    /**
     * @param warnings list of warnings
     * @return always true
     */
    @Override
    public boolean validate(List<String> warnings) {
        return true;
    }

    /**
     * Intercepts base record class generation
     *
     * @param topLevelClass     the generated base record class
     * @param introspectedTable The class containing information about the table as
     *                          introspected from the database
     * @return always true
     */
    @Override
    public boolean modelBaseRecordClassGenerated(TopLevelClass topLevelClass, IntrospectedTable introspectedTable) {
        addAnnotations(topLevelClass);
        return true;
    }

    /**
     * Intercepts primary key class generation
     *
     * @param topLevelClass     the generated primary key class
     * @param introspectedTable The class containing information about the table as
     *                          introspected from the database
     * @return always true
     */
    @Override
    public boolean modelPrimaryKeyClassGenerated(TopLevelClass topLevelClass, IntrospectedTable introspectedTable) {
        addAnnotations(topLevelClass);
        return true;
    }

    /**
     * Intercepts "record with blob" class generation
     *
     * @param topLevelClass     the generated record with BLOBs class
     * @param introspectedTable The class containing information about the table as
     *                          introspected from the database
     * @return always true
     */
    @Override
    public boolean modelRecordWithBLOBsClassGenerated(TopLevelClass topLevelClass,
                                                      IntrospectedTable introspectedTable) {
        addAnnotations(topLevelClass);
        return true;
    }

    /**
     * Prevents all getters from being generated.
     * See SimpleModelGenerator
     *
     * @param method             the getter, or accessor, method generated for the specified
     *                           column
     * @param topLevelClass      the partially implemented model class
     * @param introspectedColumn The class containing information about the column related
     *                           to this field as introspected from the database
     * @param introspectedTable  The class containing information about the table as
     *                           introspected from the database
     * @param modelClassType     the type of class that the field is generated for
     */
    @Override
    public boolean modelGetterMethodGenerated(
            Method method,
            TopLevelClass topLevelClass,
            IntrospectedColumn introspectedColumn,
            IntrospectedTable introspectedTable,
            ModelClassType modelClassType) {
        return false;
    }

    /**
     * Prevents all setters from being generated
     * See SimpleModelGenerator
     *
     * @param method             the setter, or mutator, method generated for the specified
     *                           column
     * @param topLevelClass      the partially implemented model class
     * @param introspectedColumn The class containing information about the column related
     *                           to this field as introspected from the database
     * @param introspectedTable  The class containing information about the table as
     *                           introspected from the database
     * @param modelClassType     the type of class that the field is generated for
     * @return always false
     */
    @Override
    public boolean modelSetterMethodGenerated(
            Method method,
            TopLevelClass topLevelClass,
            IntrospectedColumn introspectedColumn,
            IntrospectedTable introspectedTable,
            ModelClassType modelClassType) {
        return false;
    }

    /**
     * Adds the lombok annotations' imports and annotations to the class
     *
     * @param topLevelClass the partially implemented model class
     */
    private void addAnnotations(TopLevelClass topLevelClass) {
        for (Annotations annotation : annotations) {
            topLevelClass.addImportedType(annotation.javaType);
            topLevelClass.addAnnotation(annotation.asAnnotation());
        }
    }

    @Override
    public void setProperties(Properties properties) {
        super.setProperties(properties);

        //@Data,@Builder,@NoArgsConstructor,@AllArgsConstructor is default annotation
        annotations.add(Annotations.DATA);
        annotations.add(Annotations.BUILDER);
        annotations.add(Annotations.NO_ARGS_CONSTRUCTOR);
        annotations.add(Annotations.ALL_ARGS_CONSTRUCTOR);

        for (String annotationName : properties.stringPropertyNames()) {
            if (annotationName.contains(".")) {
                // Not an annotation name
                continue;
            }
            String value = properties.getProperty(annotationName);
            if (!Boolean.parseBoolean(value)) {
                // The annotation is disabled, skip it
                continue;
            }
            Annotations annotation = Annotations.getValueOf(annotationName);
            if (annotation == null) {
                continue;
            }
            String optionsPrefix = annotationName + ".";
            for (String propertyName : properties.stringPropertyNames()) {
                if (!propertyName.startsWith(optionsPrefix)) {
                    // A property not related to this annotation
                    continue;
                }
                String propertyValue = properties.getProperty(propertyName);
                annotation.appendOptions(propertyName, propertyValue);
                annotations.add(annotation);
                annotations.addAll(Annotations.getDependencies(annotation));
            }
        }
    }

    private enum Annotations {
        DATA("data", "@Data", "lombok.Data"),
        BUILDER("builder", "@Builder", "lombok.Builder"),
        ALL_ARGS_CONSTRUCTOR("allArgsConstructor", "@AllArgsConstructor", "lombok.AllArgsConstructor"),
        NO_ARGS_CONSTRUCTOR("noArgsConstructor", "@NoArgsConstructor", "lombok.NoArgsConstructor"),
        ACCESSORS("accessors", "@Accessors", "lombok.experimental.Accessors"),
        TO_STRING("toString", "@ToString", "lombok.ToString");


        private final String paramName;
        private final String name;
        private final FullyQualifiedJavaType javaType;
        private final List<String> options;


        Annotations(String paramName, String name, String className) {
            this.paramName = paramName;
            this.name = name;
            javaType = new FullyQualifiedJavaType(className);
            options = new ArrayList<>();
        }

        private static Annotations getValueOf(String paramName) {
            for (Annotations annotation : Annotations.values()) {
                if (String.CASE_INSENSITIVE_ORDER.compare(paramName, annotation.paramName) == 0) {
                    return annotation;
                }
            }
            return null;
        }

        private static Collection<Annotations> getDependencies(Annotations annotation) {
            if (annotation == ALL_ARGS_CONSTRUCTOR) {
                return Collections.singleton(NO_ARGS_CONSTRUCTOR);
            } else {
                return Collections.emptyList();
            }
        }

        // A trivial quoting.
        // Because Lombok annotation options type is almost String or boolean.
        private static String quote(String value) {
            if (Boolean.TRUE.toString().equals(value) || Boolean.FALSE.toString().equals(value)) {
                return value;
            }
            // case of boolean, not passed as an array.
            return value.replaceAll("[\\w]+", "\"$0\"");
        }

        private void appendOptions(String key, String value) {
            String keyPart = key.substring(key.indexOf(".") + 1);
            String valuePart = value.contains(",") ? String.format("{%s}", value) : value;
            options.add(String.format("%s=%s", keyPart, quote(valuePart)));
        }

        private String asAnnotation() {
            if (options.isEmpty()) {
                return name;
            }
            StringBuilder sb = new StringBuilder();
            sb.append(name);
            sb.append("(");
            boolean first = true;
            for (String option : options) {
                if (first) {
                    first = false;
                } else {
                    sb.append(", ");
                }
                sb.append(option);
            }
            sb.append(")");
            return sb.toString();
        }
    }
}

2. ServicePlugin 插件

主要是为了便于自动生成 Service 类

public class ServicePlugin extends PluginAdapter {

    private String targetProject;
    private String targetPackage;

    @Override
    public boolean validate(List<String> list) {
        return true;
    }

    @Override
    public void setProperties(Properties properties) {
        super.setProperties(properties);
        String targetProject = this.properties.getProperty("targetProject");
        if (StringUtility.stringHasValue(targetProject)) {
            this.targetProject = targetProject;
        } else {
            throw new RuntimeException("targetProject 属性不能为空！");
        }
        String targetPackage = this.properties.getProperty("targetPackage");
        if (StringUtility.stringHasValue(targetPackage)) {
            this.targetPackage = targetPackage;
        } else {
            throw new RuntimeException("targetPackage 属性不能为空！");
        }
    }

    /**
     * @param introspectedTable
     * @return
     */
    @Override
    public List<GeneratedJavaFile> contextGenerateAdditionalJavaFiles(IntrospectedTable introspectedTable) {
        FullyQualifiedJavaType entityType = new FullyQualifiedJavaType(introspectedTable.getBaseRecordType());
        String domainObjectName = introspectedTable.getFullyQualifiedTable().getDomainObjectName();
        String service = targetPackage + "." + domainObjectName + "Service";
        TopLevelClass topLevelClass = new TopLevelClass(new FullyQualifiedJavaType(service));
        topLevelClass.addImportedType(entityType);
        topLevelClass.addImportedType(new FullyQualifiedJavaType(service));
        topLevelClass.addImportedType(new FullyQualifiedJavaType("org.springframework.stereotype.Service"));
        topLevelClass.addImportedType(new FullyQualifiedJavaType("org.springframework.beans.factory.annotation" +
                ".Autowired"));
        topLevelClass.addImportedType(new FullyQualifiedJavaType("cn.mwee.service.base_framework.mysql.service" +
                ".BaseService"));
        topLevelClass.addAnnotation("@Service(\"" + firstLetterLowerCase(domainObjectName + "Service") + "\")");
        topLevelClass.setVisibility(JavaVisibility.PUBLIC);
        topLevelClass.setSuperClass(new FullyQualifiedJavaType("BaseService<" + entityType.getShortName() + ">"));
        setMapperField(introspectedTable, topLevelClass);
        ElementUtil.addAuthorTag(topLevelClass);
        return Arrays.asList(new GeneratedJavaFile(topLevelClass, targetProject, new DefaultJavaFormatter()));
    }

    /**
     * @param introspectedTable
     * @param clazz
     */
    private void setMapperField(IntrospectedTable introspectedTable, TopLevelClass clazz) {
        // 实体类的类名
        String domainObjectName = introspectedTable.getFullyQualifiedTable().getDomainObjectName();
        // Mapper类所在包的包名
        String mapperPackage = introspectedTable.getContext().getJavaClientGeneratorConfiguration().getTargetPackage();
        Field mapperField = new Field();
        // 设置Field的注解
        mapperField.addAnnotation("@Autowired");
        mapperField.setVisibility(JavaVisibility.PRIVATE);
        // 设置Field的类型
        mapperField.setType(new FullyQualifiedJavaType(domainObjectName + "Mapper"));
        // 设置Field的名称
        mapperField.setName(firstLetterLowerCase(domainObjectName) + "Mapper");
        // 将Field添加到对应的类中
        clazz.addField(mapperField);
        // 对应的类需要import Mapper类(使用全限定类名)
        clazz.addImportedType(new FullyQualifiedJavaType(mapperPackage + "." + domainObjectName + "Mapper"));
    }

    private String firstLetterLowerCase(String name) {
        char c = name.charAt(0);
        if (c >= 'A' && c <= 'Z') {
            String temp = String.valueOf(c);
            return name.replaceFirst(temp, temp.toLowerCase());
        }
        return name;
    }
}

3. 解决数据库 Unsigned 类型字段

使用官方 mybatis generator 1.3.7 版本自动生产的实体类映射，是不能区分 Unsigned 和 Signed mysql 8.x（针对 java 项目，很容易出现类型字段溢出），尤其实际项目中，接手老的项目，之前一些数据库字段的设置，留下来的一些“坑”；

• 官方方案：（github 上也有一些小伙伴提了相应的 issue，好像没有 fixed）

  <columnOverride> 元素覆盖指定的字段
  缺点：在针对很多表的时候，都需要手动设置这些字段，而且很容易丢失（可能导致线上问题）

• 解决方案：

  通过 download 官方 mybatis generator 源码，发现是可以自动识别 Unsigned 和 Signed 字段属性的，故修改了源码，打包，重新编译，达到了想要的目的，不需要针对指定的字段每一个修改（在 github 上已经和官方作者沟通，接受了 issue，将于下一个版本 1.4.0 做增强），由于官方作者一直没发布 1.4.0，故公司内部打包如下 Jar 版本：mybatis-generator-maven-plugin-1.3.7.2.jar

4. 如何自动生成 jdk8 时间映射

之前是打算直接写插件直接自动生成，但是考虑到有些项目还是用的 jdk8 以前的时间，老的项目也不能强制要求 jdk8 时间版本，故下面 👇 只是展示如何处理.

在生成的实体类中加入下面处理

<columnOverride column="created_time" property="createdTime"
                            typeHandler="org.apache.ibatis.type.LocalDateTimeTypeHandler"
                            jdbcType="OTHER" javaType="java.time.LocalDateTime"/>
<columnOverride column="updated_time" property="updatedTime"
                            typeHandler="org.apache.ibatis.type.LocalDateTimeTypeHandler"
                            jdbcType="OTHER" javaType="java.time.LocalDateTime"/>

注：在 mybatis 使用 jdk8 时间时，需要注意的是，mybatis 3.5.1+和 druid 1.1.20 是不支持 jdk8 的时间戳的druid-jdk8，不过，现在已经修复了，等下一个版本估计就能解决了（当然，也可以切换到 HikariCP 数据源）

5. 集成 gradle 插件

市场上已经有很多 gradle 集成 mybatis generator，选择了其中一个比较好用的插件mybatis-generator-plugin（尊重原创作者），当然在公司内部处理，也针对这个插件做了相应的修改定制

6. 附录

针对上面 👆 的一些处理，生成的结构图如下：

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