Mybatis generator生成工具简单介绍

其主要的功能就是方便，快捷的创建好Dao，entry，xml 加快了开发速度，使用方面根据其提供的规则配置好就OK

　　这里还有一个重要的开发场景，开发过程中，对数据库的操作肯定很多，比如新增字段什么的，你只要将原先自动生成的一套代码删除，重新再生成一份，这就完美解决了，但是这样做的前提是，你必须对生成后的代码不改动，只是使用。不需要想手动开发写代码那样到处改代码，还担心改漏地方。

　　其实这个的实现方式也是五花八门的，写一种比较常见的

 主要流程

　　第一步：添加依赖

　　主要是jdbc和generator

<!-- https://mvnrepository.com/artifact/org.mybatis.generator/mybatis-generator-core -->
<dependency>
    <groupId>org.mybatis.generator</groupId>
    <artifactId>mybatis-generator-core</artifactId>
    <version>1.3.6</version>
</dependency>

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.38</version>
</dependency>

　  第二步：配置 generatorConfig.xml 

　  这个文件主要是对  从哪来，到哪去的描述，还有一些特殊要求的配置

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
    <context id="DB2Tables" targetRuntime="MyBatis3">
        <!-- 生成mysql带有分页的sql的插件  这个可以自己写，-->
        <plugin type="generator.MysqlPaginationPlugin" />
        <plugin type="org.mybatis.generator.plugins.ToStringPlugin" />
        <plugin type="org.mybatis.generator.plugins.SerializablePlugin" />
        <!-- 自定义的注释规则，继承 DefaultCommentGenerator 重写 一些方法 -->
        <commentGenerator type="generator.NewbatisGenerator">
            <!-- 是否去除自动生成日期的注释 true：是 ： false:否 -->
            <property name="suppressDate" value="true"/>
            <!-- 是否去除所有自动生成的注释 true：是 ： false:否 -->
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://数据库地址"
                        userId="username"
                        password="password">
        </jdbcConnection>
        <!--生成entity类存放位置-->
        <javaModelGenerator targetPackage="包名（com.generator.test.entity）" targetProject="项目地址到java （D:workspacesrcmainjava）">
            <property name="enableSubPackages" value="true"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>
        <!--生成映射文件存放位置-->
        <sqlMapGenerator targetPackage="包名（com.generator.test.mapper）" targetProject="项目地址到java （D:workspacesrcmainjava）">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>
        <!--生成Dao类存放位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="包名（com.generator.test.dao）"
                             targetProject="项目地址到java （D:workspacesrcmainjava）">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>
        <table tableName="表名" domainObjectName="生成实体的类名">
        </table>
    </context>
</generatorConfiguration>

　　第三步：主要看你个人的需求，对注释，分页啥的有啥要求不，可以重写几个方法对其进行改造

　　主要举几个例子  

　　对注释的修改 NewbatisGenerator 

public class NewbatisGenerator extends DefaultCommentGenerator {
    private Properties properties;
    private Properties systemPro;
    private boolean suppressDate;
    private boolean suppressAllComments;
    private String currentDateStr;

    public NewbatisGenerator() {
        super();
        properties = new Properties();
        systemPro = System.getProperties();
        suppressDate = false;
        suppressAllComments = false;
        currentDateStr = (new SimpleDateFormat("yyyy-MM-dd")).format(new Date());
    }

    /**
     * 对类的注解
     * @param topLevelClass
     * @param introspectedTable
     */
    @Override
    public void addModelClassComment(TopLevelClass topLevelClass, IntrospectedTable introspectedTable) {
        topLevelClass.addJavaDocLine("/**");
        topLevelClass.addJavaDocLine(" * 这是MyBatis Generator自动生成的Model Class.");

        StringBuilder sb = new StringBuilder();
        sb.append(" * 对应的数据表是 : ");
        sb.append(introspectedTable.getFullyQualifiedTable());
        topLevelClass.addJavaDocLine(sb.toString());

        String tableRemarks = introspectedTable.getRemarks();
        if (!StringUtils.isEmpty(tableRemarks)) {
            sb.setLength(0);
            sb.append(" * 数据表注释 : ");
            sb.append(tableRemarks);
            topLevelClass.addJavaDocLine(sb.toString());
        }

        sb.setLength(0);
        sb.append(" * @author ");
        sb.append(systemPro.getProperty("user.name"));
        topLevelClass.addJavaDocLine(sb.toString());

        String curDateString = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")).format(new Date());
        sb.setLength(0);
        sb.append(" * @date ");
        sb.append(curDateString);
        topLevelClass.addJavaDocLine(sb.toString());

        topLevelClass.addJavaDocLine(" */");
    }

    /**
     * 生成的实体增加字段的中文注释
     */
    public void addFieldComment(Field field, IntrospectedTable introspectedTable,
                                IntrospectedColumn introspectedColumn) {
        if (suppressAllComments) {
            return;
        }
        StringBuilder sb = new StringBuilder();
        field.addJavaDocLine("/**");
        sb.append(" * ");
        sb.append(introspectedColumn.getRemarks());
        field.addJavaDocLine(sb.toString().replace("
", " "));
        field.addJavaDocLine(" */");
    }

}

对分页的添加  MysqlPaginationPlugin  自动生成带分页插件

public class MysqlPaginationPlugin extends PluginAdapter {
    public MysqlPaginationPlugin() {}

    public boolean modelExampleClassGenerated(TopLevelClass topLevelClass,
            IntrospectedTable introspectedTable) {
        this.addLimit(topLevelClass, introspectedTable, "limitStart");
        this.addLimit(topLevelClass, introspectedTable, "limitSize");
        return super.modelExampleClassGenerated(topLevelClass, introspectedTable);
    }

    public boolean sqlMapSelectByExampleWithoutBLOBsElementGenerated(XmlElement element,
            IntrospectedTable introspectedTable) {
        XmlElement isNotNullElement = new XmlElement("if");
        isNotNullElement
                .addAttribute(new Attribute("test", "limitStart != null and limitSize >= 0"));
        isNotNullElement.addElement(new TextElement("limit #{limitStart} , #{limitSize}"));
        element.addElement(isNotNullElement);
        return super.sqlMapSelectByExampleWithoutBLOBsElementGenerated(element, introspectedTable);
    }

    public boolean sqlMapSelectByExampleWithBLOBsElementGenerated(XmlElement element,
            IntrospectedTable introspectedTable) {
        XmlElement isNotNullElement = new XmlElement("if");
        isNotNullElement
                .addAttribute(new Attribute("test", "limitStart != null and limitSize >= 0"));
        isNotNullElement.addElement(new TextElement("limit #{limitStart} , #{limitSize}"));
        element.addElement(isNotNullElement);
        return super.sqlMapSelectByExampleWithBLOBsElementGenerated(element, introspectedTable);
    }

    private void addLimit(TopLevelClass topLevelClass, IntrospectedTable introspectedTable,
            String name) {
        CommentGenerator commentGenerator = this.context.getCommentGenerator();
        Field field = new Field();
        field.setVisibility(JavaVisibility.PROTECTED);
        field.setType(PrimitiveTypeWrapper.getIntegerInstance());
        field.setName(name);
        commentGenerator.addFieldComment(field, introspectedTable);
        topLevelClass.addField(field);
        char c = name.charAt(0);
        String camel = Character.toUpperCase(c) + name.substring(1);
        Method method = new Method();
        method.setVisibility(JavaVisibility.PUBLIC);
        method.setName("set" + camel);
        method.addParameter(new Parameter(PrimitiveTypeWrapper.getIntegerInstance(), name));
        StringBuilder sb = new StringBuilder();
        sb.append("this.");
        sb.append(name);
        sb.append(" = ");
        sb.append(name);
        sb.append(";");
        method.addBodyLine(sb.toString());
        commentGenerator.addGeneralMethodComment(method, introspectedTable);
        topLevelClass.addMethod(method);
        Method getterMethod = AbstractJavaGenerator.getGetter(field);
        commentGenerator.addGeneralMethodComment(getterMethod, introspectedTable);
        topLevelClass.addMethod(getterMethod);
    }

    public boolean validate(List<String> warnings) {
        return true;
    }



    /**
     * 生成mapper.xml,文件内容会被清空再写入
     * */
    @Override
    public boolean sqlMapGenerated(GeneratedXmlFile sqlMap, IntrospectedTable introspectedTable) {
        sqlMap.setMergeable(false);
        return super.sqlMapGenerated(sqlMap, introspectedTable);
    }

}

　　最后一步：运行生成

　　这些官网都是有的

public class Generator {

    public static void main(String[] args) throws Exception{
        List<String> warnings = new ArrayList<String>();
        boolean overwrite = true;
        File configFile = new File("generatorConfig.xml");
        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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