讓MyBatis Generator產生的Mapper更簡潔
本文提供一種方法，目標是讓MyBatis Generator產生的Mapper更簡潔。html
主要體如今以下幾個方面：java
- 有一個BaseMapper（本身編寫）
- 全部產生的Mapper繼承BaseMapper，無需每一個Mapper都要定義好多接口方法
- 除了產生的Mapper有改動以外，其他自動產生的Entity、Example、XML文件保持不變
背景
不一樣Mapper的內容比較
好比，咱們創建兩個測試表，一個是t_user, 一個是t_news。其建表語句以下：sql
CREATE TABLE `t_user` ( `user_id` int(11) NOT NULL AUTO_INCREMENT, `email` varchar(64) DEFAULT NULL, `name` varchar(30) DEFAULT NULL, PRIMARY KEY (`user_id`) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
CREATE TABLE `t_news` ( `news_id` int(11) NOT NULL AUTO_INCREMENT, `title` varchar(150) NOT NULL, `content` text NOT NULL, `brief_intro` varchar(255) DEFAULT NULL, `pic_url` varchar(255) DEFAULT NULL, `news_from` varchar(100) DEFAULT NULL, `news_author` varchar(50) DEFAULT NULL, `news_url` varchar(255) DEFAULT NULL, `keywords` varchar(150) DEFAULT NULL, `meta_desc` varchar(150) DEFAULT NULL, `create_time` datetime DEFAULT NULL, PRIMARY KEY (`news_id`) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8
而後，咱們比較一下自動產生的Mapper有什麼區別？數據庫
UserMapper.javaapache
import java.util.List;
import my.mybatis.generator.auto.entity.User;
import my.mybatis.generator.auto.entity.UserExample;
import org.apache.ibatis.annotations.Param;
public interface UserMapper {
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int countByExample(UserExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int deleteByExample(UserExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int deleteByPrimaryKey(Integer userId);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int insert(User record);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int insertSelective(User record);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
List<User> selectByExample(UserExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
User selectByPrimaryKey(Integer userId);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByExampleSelective(@Param("record") User record, @Param("example") UserExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByExample(@Param("record") User record, @Param("example") UserExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByPrimaryKeySelective(User record);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table t_user
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByPrimaryKey(User record);
}
NewsMapper.javaapi
import java.util.List;
import my.mybatis.generator.auto.entity.News;
import my.mybatis.generator.auto.entity.NewsExample;
import org.apache.ibatis.annotations.Param;
public interface NewsMapper {
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int countByExample(NewsExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int deleteByExample(NewsExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int deleteByPrimaryKey(Integer newsId);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int insert(News record);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int insertSelective(News record);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
List<News> selectByExampleWithBLOBs(NewsExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
List<News> selectByExample(NewsExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
News selectByPrimaryKey(Integer newsId);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByExampleSelective(@Param("record") News record, @Param("example") NewsExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByExampleWithBLOBs(@Param("record") News record, @Param("example") NewsExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByExample(@Param("record") News record, @Param("example") NewsExample example);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByPrimaryKeySelective(News record);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByPrimaryKeyWithBLOBs(News record);
/**
* This method was generated by MyBatis Generator.
* This method corresponds to the database table m_news
*
* @mbggenerated Wed Nov 09 10:23:34 CST 2016
*/
int updateByPrimaryKey(News record);
}
從上述兩個自動產生的Mapper能夠看出，session
除了Entity、Entity對應的Example以及Primary Key可能會變化以外，其他全部的方法名都是同樣的。mybatis
分析
若是是這樣自動產生代碼，那麼各個Mapper勢必有不少重複的代碼，不直觀。app
那麼，問題來了？dom
可不能夠將這些通用的方法定義在一個BaseMapper中，而後，其他自動產生的Mapper繼承自BaseMapper，且與各自的Entity、Example、Primary KEY綁定在一塊兒呢？
好比：
定義一個BaseMapper.java，其中，
- T表示與table表對應的實體類（Entity）
- E表示Entity對應的Example類
- PK表示可能會用到主鍵 (好比Integer等)
以下所示：
package my.mabatis.example.base;
import java.io.Serializable;
import java.util.List;
import org.apache.ibatis.annotations.Param;
/**
*
* @author wangmengjun
*
*/
public interface BaseMapper<T, E, PK extends Serializable> {
long countByExample(E example);
int deleteByExample(E example);
int deleteByPrimaryKey(PK pk);
int insert(T record);
int insertSelective(T record);
List<T> selectByExample(E example);
T selectByPrimaryKey(PK pk);
int updateByExampleSelective(@Param("record") T record,
@Param("example") E example);
int updateByExample(@Param("record") T record, @Param("example") E example);
int updateByPrimaryKeySelective(T record);
int updateByPrimaryKey(T record);
}
那麼，
UserMapper.java就變成相似以下的樣子了。
public interface NewsMapper extends BaseMapper<News, NewsExample, Integer> {
}
接下來，咱們就來看看如何完成去達到這樣的目標。Let‘s GO~~~~
解決方法
改源代碼
改源代碼？
若是一個工具，讓產生的Dao繼承一個BaseMapper，都須要經過源碼來完成，那其擴展性可見通常。 不建議使用，這個只能是沒有辦法的時候纔會使用。
由於，上述考慮的都是Mapper，那麼，若是改動源代碼的話，咱們就在org.mybatis.generator.codegen.mybatis3.javamapper.JavaMapperGenerator類中修改便可。
修改包含兩個部分，
- 不在Mapper中添加任何方法，由於這些都在BaseMapper中存在了，只要繼承便可。
- 產生Mapper的時候，指定父類接口BaseMapper, 實體類類型、Example類型、主鍵類型。
具體在JavaMapperGenerator類的getCompilationUnits方法下進行：
public List<CompilationUnit> getCompilationUnits() {
//省略全部方法內容
}
- 移除添加方法的代碼
addCountByExampleMethod(interfaze);
addDeleteByExampleMethod(interfaze);
addDeleteByPrimaryKeyMethod(interfaze);
addInsertMethod(interfaze);
addInsertSelectiveMethod(interfaze);
addSelectByExampleWithBLOBsMethod(interfaze);
addSelectByExampleWithoutBLOBsMethod(interfaze);
addSelectByPrimaryKeyMethod(interfaze);
addUpdateByExampleSelectiveMethod(interfaze);
addUpdateByExampleWithBLOBsMethod(interfaze);
addUpdateByExampleWithoutBLOBsMethod(interfaze);
addUpdateByPrimaryKeySelectiveMethod(interfaze);
addUpdateByPrimaryKeyWithBLOBsMethod(interfaze);
addUpdateByPrimaryKeyWithoutBLOBsMethod(interfaze);
- 指定父類接口BaseMapper, 實體類類型等
在上述移除的代碼塊中添加相似以下代碼塊。
/**
* 主鍵默認採用java.lang.Integer
*/
FullyQualifiedJavaType fqjt = new FullyQualifiedJavaType("BaseMapper<"
+ introspectedTable.getBaseRecordType() + ","
+ introspectedTable.getExampleType() + ","
+ "java.lang.Integer" + ">");
FullyQualifiedJavaType imp = new FullyQualifiedJavaType(
"my.mabatis.example.base.BaseMapper");
/**
* 添加 extends MybatisBaseMapper
*/
interfaze.addSuperInterface(fqjt);
/**
* 添加import my.mabatis.example.base.MybatisBaseMapper;
*/
interfaze.addImportedType(imp);
/**
* 方法不須要
*/
interfaze.getMethods().clear();
而後，而後就搞定了。 : )
不改源代碼？
儘管修改源代碼的方式可行，可是侵入性太強。
其實，MyBatis Generator自動代碼產生工具已經提供插件適配擴展的功能，咱們只要繼承PluginAdapter便可。而後，重寫clientGenerated方法便可。
@Override
public boolean clientGenerated(Interface interfaze,
TopLevelClass topLevelClass, IntrospectedTable introspectedTable) {
}
具體代碼以下：
默認採用java.lang.Integer做爲主鍵。
package my.mabatis.example.plugin;
import java.util.List;
import org.mybatis.generator.api.IntrospectedTable;
import org.mybatis.generator.api.PluginAdapter;
import org.mybatis.generator.api.dom.java.FullyQualifiedJavaType;
import org.mybatis.generator.api.dom.java.Interface;
import org.mybatis.generator.api.dom.java.TopLevelClass;
/**
* @author wangmengjun
*
*/
public class BaseMapperGeneratorPlugin extends PluginAdapter {
public boolean validate(List<String> warnings) {
return true;
}
/**
* 生成dao
*/
@Override
public boolean clientGenerated(Interface interfaze,
TopLevelClass topLevelClass, IntrospectedTable introspectedTable) {
/**
* 主鍵默認採用java.lang.Integer
*/
FullyQualifiedJavaType fqjt = new FullyQualifiedJavaType("BaseMapper<"
+ introspectedTable.getBaseRecordType() + ","
+ introspectedTable.getExampleType() + ","
+ "java.lang.Integer" + ">");
FullyQualifiedJavaType imp = new FullyQualifiedJavaType(
"my.mabatis.example.base.BaseMapper");
/**
* 添加 extends MybatisBaseMapper
*/
interfaze.addSuperInterface(fqjt);
/**
* 添加import my.mabatis.example.base.MybatisBaseMapper;
*/
interfaze.addImportedType(imp);
/**
* 方法不須要
*/
interfaze.getMethods().clear();
interfaze.getAnnotations().clear();
return true;
}
}
接着，在用於自動產生代碼的配置文件中generatorConfig.xml指定自定義的plugin。
如：
<!-- 配置內置的或者自定義的Plugin -->
<plugin type="my.mabatis.example.plugin.BaseMapperGeneratorPlugin" />
詳細配置如：
<?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>
<!-- 引入配置文件 -->
<properties resource="jdbc.properties" />
<context id="context1" targetRuntime="MyBatis3">
<!-- 配置內置的或者自定義的Plugin -->
<plugin type="my.mabatis.example.plugin.BaseMapperGeneratorPlugin" />
<!-- 註釋產生配置 -->
<commentGenerator>
<property name="suppressAllComments" value="false" />
<property name="suppressDate" value="false" />
</commentGenerator>
<!-- 數據庫鏈接信息 -->
<jdbcConnection driverClass="${jdbc.driverClassName}"
connectionURL="${jdbc.url}" userId="${jdbc.username}" password="${jdbc.password}" />
<!-- 生成Model對象路徑配置 -->
<javaModelGenerator targetPackage="my.mybatis.generator.auto.entity"
targetProject="src\main\java">
<property name="enableSubPackages" value="true" />
<property name="trimStrings" value="true" />
</javaModelGenerator>
<!-- 生成sqlXML文件路徑配置 -->
<sqlMapGenerator targetPackage="my.mybatis.generator.auto.entity.xml"
targetProject="src\main\java">
<property name="enableSubPackages" value="true" />
</sqlMapGenerator>
<!-- 生成DAO的類文件路徑配置 -->
<javaClientGenerator targetPackage="my.mybatis.generator.auto.dao"
targetProject="src\main\java" type="XMLMAPPER">
<property name="enableSubPackages" value="true" />
</javaClientGenerator>
<!--要生成哪些表 -->
<table tableName="t_user" domainObjectName="User" />
<table tableName="t_news" domainObjectName="News" />
</context>
</generatorConfiguration>
通過上述幾個步驟，從新生成代碼，就能夠看到生成的Mapper，包括UserMapper和NewsMapper都已經發生了變化，而這正是咱們所指望的。
public interface NewsMapper extends BaseMapper<News, NewsExample, Integer> {
}
public interface UserMapper extends BaseMapper<User, UserExample, Integer> {
}
自動產生的Mapper繼承於BaseMapper，變得相對較爲乾淨。
接下來，咱們就來測試一下，是否管用。
測試驗證
建立mybatis-config.xml文件
在src/main/resource目錄下建立mybatis-config.xml配置文件。內容以下：
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="jdbc.properties" />
<typeAliases>
<typeAlias type="my.mybatis.generator.auto.entity.User"
alias="User" />
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driverClassName}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="my/mybatis/generator/auto/entity/xml/UserMapper.xml" />
</mappers>
</configuration>
建立一個MyBatisUtil工具類
package my.mabatis.example.util;
import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
/**
*
* @author wangmengjun
*
*/
public class MyBatisUtil {
private static SqlSessionFactory factory;
private MyBatisUtil() {
}
static {
Reader reader = null;
try {
reader = Resources.getResourceAsReader("mybatis-config.xml");
} catch (IOException e) {
throw new RuntimeException(e.getMessage());
}
factory = new SqlSessionFactoryBuilder().build(reader);
}
public static SqlSessionFactory getSqlSessionFactory() {
return factory;
}
}
編寫Service類
由於只是很簡單的操做，因此service就不分接口和實現了，直接上代碼。
package my.mabatis.example.service;
import java.util.List;
import my.mabatis.example.util.MyBatisUtil;
import my.mybatis.generator.auto.dao.UserMapper;
import my.mybatis.generator.auto.entity.User;
import my.mybatis.generator.auto.entity.UserExample;
import my.mybatis.generator.auto.entity.UserExample.Criteria;
import org.apache.ibatis.session.SqlSession;
/**
*
* @author wangmengjun
*
*/
public class UserService {
/**
* 保存用戶
* @param user 待保存用戶對象
*/
public void insertUser(User user) {
SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory()
.openSession();
try {
UserMapper userDao = sqlSession.getMapper(UserMapper.class);
userDao.insert(user);
sqlSession.commit();
} finally {
sqlSession.close();
}
}
/**
* 按照指定email返回用戶
* @param email
* @return 按照指定email返回用戶
*/
public User findUserByEmail(String email) {
SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory()
.openSession();
try {
UserMapper userDao = sqlSession.getMapper(UserMapper.class);
/**
* 使用Example來操做
*/
UserExample example = new UserExample();
Criteria criteria = example.createCriteria();
criteria.andEmailEqualTo(email);
List<User> users = userDao.selectByExample(example);
/**
* 假定email惟一
*/
return users.isEmpty() ? null : users.get(0);
} finally {
sqlSession.close();
}
}
}
測試類和運行結果
package my.mabatis.example.runner;
import my.mabatis.example.service.UserService;
import my.mybatis.generator.auto.entity.User;
public class Test {
public static void main(String[] args) {
UserService userService = new UserService();
User userToInsert = new User();
userToInsert.setEmail("wmj123456@test.com");
userToInsert.setName("mengjun");
userService.insertUser(userToInsert);
User user = userService.findUserByEmail("wmj123456@test.com");
System.out.println(user.getEmail());
System.out.println(user.getName());
}
}
輸出結果：
log4j:WARN No appenders could be found for logger (org.apache.ibatis.logging.LogFactory). log4j:WARN Please initialize the log4j system properly. log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info. wmj123456@test.com mengjun
保存用戶信息和查看用戶信息都能成功執行，代碼可用。至此，整個流程就結束了。
Note:
整個代碼都是在上一篇文章<<使用MyBatis Generator自動生成代碼>>的基礎上改動的，如對generatorConfig.xml等配置文件或者對如何自動產生代碼有疑問，能夠參考一下。
工程結構
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相關文章
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