Mybatis自动生成工具能够根据数据库表/视图等自动生成相应的bean和mapper，大大的简化了开发工作。
但默认的生成bean并没有将数据库表中的字段注释也放到生成的bean的属性上。
本文记录如何让mybatis-generator根据数据库表字段注释生成bean的属性注释。

一.编写自定义注释生成工具

首先我们要实现CommentGenerator这个接口，编写一个自定义注释生成工具
当然也可以继承DefaultCommentGenerator这个类，直接重写getter、setter、字段等生成注释的方法即可。

import org.mybatis.generator.api.CommentGenerator;
import org.mybatis.generator.api.IntrospectedColumn;
import org.mybatis.generator.api.IntrospectedTable;
import org.mybatis.generator.api.dom.java.*;
import org.mybatis.generator.api.dom.xml.XmlElement;
import org.mybatis.generator.config.MergeConstants;
import org.mybatis.generator.config.PropertyRegistry;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Properties;

/**
 * @author HelSing
 * @date 2019/3/18
 */
public class MybatisCommentGenerator implements CommentGenerator {

    private Properties properties;
    private Properties systemPro;
    private boolean suppressDate;
    private boolean suppressAllComments;
    private String nowTime;

    public MybatisCommentGenerator() {
        super();
        properties = new Properties();
        systemPro = System.getProperties();
        suppressDate = false;
        suppressAllComments = false;
        nowTime = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")).format(new Date());
    }


    /**
     * 类的注释
     * @param innerClass
     * @param introspectedTable
     * @param markAsDoNotDelete
     */
    @Override
    public void addClassComment(InnerClass innerClass, IntrospectedTable introspectedTable, boolean markAsDoNotDelete) {
        if (suppressAllComments) {
            return;
        }
        StringBuilder sb = new StringBuilder();
        innerClass.addJavaDocLine("/**");
        sb.append(" * ");
        sb.append(introspectedTable.getFullyQualifiedTable());
        innerClass.addJavaDocLine(sb.toString().replace("\n", " "));
        sb.setLength(0);
        sb.append(" * @author ");
        sb.append(systemPro.getProperty("user.name"));
        sb.append(" ");
        sb.append(nowTime);
        innerClass.addJavaDocLine(" */");
    }

    @Override
    public void addClassComment(InnerClass innerClass, IntrospectedTable introspectedTable) {
        if (suppressAllComments) {
            return;
        }
        StringBuilder sb = new StringBuilder();
        innerClass.addJavaDocLine("/**");
        sb.append(" * ");
        sb.append(introspectedTable.getFullyQualifiedTable());
        sb.append(" ");
        sb.append(getDateString());
        innerClass.addJavaDocLine(sb.toString().replace("\n", " "));
        innerClass.addJavaDocLine(" */");
    }

    /**
     * 设置字段注释
     */
    @Override
    public void addFieldComment(Field field, IntrospectedTable introspectedTable, IntrospectedColumn introspectedColumn) {
        if (suppressAllComments) {
            return;
        }
        StringBuilder sb = new StringBuilder();
        field.addJavaDocLine("/**");
        sb.append(" * ");
        sb.append(introspectedColumn.getRemarks() + " " + introspectedColumn.getActualColumnName());
        field.addJavaDocLine(sb.toString().replace("\n", " "));
        field.addJavaDocLine(" */");
    }

    @Override
    public void addFieldComment(Field field, IntrospectedTable introspectedTable) {
        if (suppressAllComments) {
            return;
        }
        StringBuilder sb = new StringBuilder();
        field.addJavaDocLine("/**");
        sb.append(" * ");
        sb.append(introspectedTable.getFullyQualifiedTable());
        field.addJavaDocLine(sb.toString().replace("\n", " "));
        field.addJavaDocLine(" */");
    }

    /**
     * 设置setter方法注释
     */
    @Override
    public void addSetterComment(Method method, IntrospectedTable introspectedTable,
                                 IntrospectedColumn introspectedColumn) {
        if (suppressAllComments) {
            return;
        }
        method.addJavaDocLine("/**");
        StringBuilder sb = new StringBuilder();
        sb.append(" * ");
        sb.append(introspectedColumn.getRemarks());
        method.addJavaDocLine(sb.toString().replace("\n", " "));
        sb.setLength(0);
        sb.append(" * @author ");
        sb.append(systemPro.getProperty("user.name"));
        method.addJavaDocLine(sb.toString().replace("\n", " "));
        sb.setLength(0);
        if(suppressDate){
            sb.append(" * @date " + nowTime);
            method.addJavaDocLine(sb.toString().replace("\n", " "));
            sb.setLength(0);
        }
        Parameter parm = method.getParameters().get(0);
        sb.append(" * @param ");
        sb.append(parm.getName());
        sb.append(" ");
        sb.append(introspectedColumn.getRemarks());
        method.addJavaDocLine(sb.toString().replace("\n", " "));
        method.addJavaDocLine(" */");
    }

    /**
     * 设置getter方法注释
     */
    @Override
    public void addGetterComment(Method method, IntrospectedTable introspectedTable,
                                 IntrospectedColumn introspectedColumn) {
        if (suppressAllComments) {
            return;
        }
        method.addJavaDocLine("/**");
        StringBuilder sb = new StringBuilder();
        sb.append(" * ");
        sb.append(introspectedColumn.getRemarks());
        method.addJavaDocLine(sb.toString().replace("\n", " "));
        sb.setLength(0);
        sb.append(" * @author ");
        sb.append(systemPro.getProperty("user.name"));
        method.addJavaDocLine(sb.toString().replace("\n", " "));
        sb.setLength(0);
        if(suppressDate){
            sb.append(" * @date " + nowTime);
            method.addJavaDocLine(sb.toString().replace("\n", " "));
            sb.setLength(0);
        }
        sb.append(" * @return ");
        sb.append(introspectedColumn.getActualColumnName());
        sb.append(" ");
        sb.append(introspectedColumn.getRemarks());
        method.addJavaDocLine(sb.toString().replace("\n", " "));
        method.addJavaDocLine(" */");
    }

    @Override
    public void addJavaFileComment(CompilationUnit compilationUnit) {
        if (suppressAllComments) {
            return;
        }
        return;
    }

    @Override
    public void addComment(XmlElement xmlElement) {
        return;
    }

    @Override
    public void addRootComment(XmlElement rootElement) {
        return;
    }

    @Override
    public void addConfigurationProperties(Properties properties) {
        this.properties.putAll(properties);
        suppressDate = Boolean.valueOf(properties.getProperty(PropertyRegistry.COMMENT_GENERATOR_SUPPRESS_DATE));
        suppressAllComments = Boolean.valueOf(properties.getProperty(PropertyRegistry.COMMENT_GENERATOR_SUPPRESS_ALL_COMMENTS));
    }

    protected void addJavadocTag(JavaElement javaElement, boolean markAsDoNotDelete) {
        javaElement.addJavaDocLine(" *");
        StringBuilder sb = new StringBuilder();
        sb.append(" * ");
        sb.append(MergeConstants.NEW_ELEMENT_TAG);
        if (markAsDoNotDelete) {
            sb.append(" do_not_delete_during_merge");
        }
        String s = getDateString();
        if (s != null) {
            sb.append(' ');
            sb.append(s);
        }
        javaElement.addJavaDocLine(sb.toString());
    }

    protected String getDateString() {
        String result = null;
        if (!suppressDate) {
            result = nowTime;
        }
        return result;
    }

    @Override
    public void addEnumComment(InnerEnum innerEnum, IntrospectedTable introspectedTable) {
        if (suppressAllComments) {
            return;
        }
        StringBuilder sb = new StringBuilder();
        innerEnum.addJavaDocLine("/**");
        sb.append(" * ");
        sb.append(introspectedTable.getFullyQualifiedTable());
        innerEnum.addJavaDocLine(sb.toString().replace("\n", " "));
        innerEnum.addJavaDocLine(" */");
    }

    @Override
    public void addGeneralMethodComment(Method method, IntrospectedTable introspectedTable) {
        if (suppressAllComments) {
            return;
        }
        method.addJavaDocLine("/**");
        addJavadocTag(method, false);
        method.addJavaDocLine(" */");
    }
}

二.使用第一步编写的自定义注释生成工具

在mybatis-generator的配置文件generatorConfig.xml中配置好自定义的注释生成工具

<generatorConfiguration>
<context id="default" targetRuntime="MyBatis3">
        <!-- optional，旨在创建class时，对注释进行控制 -->
        <commentGenerator type="com.xxx.generator.MybatisCommentGenerator">
            <!--<property name="suppressDate" value="true"/>-->
            <!--<property name="suppressAllComments" value="true" />-->
            <!-- 是否生成注释代时间戳-->
            <property name="suppressDate" value="true"/>
        </commentGenerator>
    </context>
</generatorConfiguration>

三.还是按照以前的生成操作执行即可

public class Organization extends BaseBean {
    /**
     * 主键ID id
     */
    private Integer id;

    /**
     * 父级ID pid
     */
    private Integer pid;

    /**
     * 机构名称 name
     */
    private String name;

    /**
     * 主键ID
     * @author Helsing
     * @date 2019-04-06 15:48:47
     * @return id 主键ID
     */
    public Integer getId() {
        return id;
    }

    /**
     * 主键ID
     * @author Helsing
     * @date 2019-04-06 15:48:47
     * @param id 主键ID
     */
    public void setId(Integer id) {
        this.id = id;
    }

    /**
     * 父级ID
     * @author Helsing
     * @date 2019-04-06 15:48:47
     * @return pid 父级ID
     */
    public Integer getPid() {
        return pid;
    }

    /**
     * 父级ID
     * @author Helsing
     * @date 2019-04-06 15:48:47
     * @param pid 父级ID
     */
    public void setPid(Integer pid) {
        this.pid = pid;
    }
}

四.参考

Mybatis自动生成字段注释