Java+MyBatis+MySQL开发环境搭建流程详解
主要搭建过程
1.pom.xml文件中加入mybatis和数据库依赖，这里使用mysql：
<properties>
<mybatis.version>3.2.3</mybatis.version>
<mysql.version>5.1.26</mysql.version>
<slf4j.api.version>1.7.5</slf4j.api.version>
<testng.version>6.8.7</testng.version>
</properties>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>${mybatis.version}</version>
</dependency>
<!--Databasedriver-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>${mysql.version}</version>
</dependency>
<!--mybatis启动要加载log4j-->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>${slf4j.api.version}</version>
</dependency>
<!--Test-->
<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<version>${testng.version}</version>
</dependency>
</dependencies>
2.在类路径下创建mybatis的配置文件Configuration.xml
<?xmlversion="1.0"encoding="UTF-8"?> <!DOCTYPEconfigurationPUBLIC"-//mybatis.org//DTDConfig3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <typeAliases><!--别名--> <typeAliasalias="User"type="com.john.hbatis.model.User"/> </typeAliases> <environmentsdefault="development"> <environmentid="development"> <transactionManagertype="JDBC"/> <dataSourcetype="POOLED"><!--数据源--> <propertyname="driver"value="com.mysql.jdbc.Driver"/> <propertyname="url"value="jdbc:mysql://localhost:3306/hbatis"/> <propertyname="username"value="root"/> <propertyname="password"value="123456"/> </dataSource> </environment> </environments> <mappers><!--ORM映射文件--> <mapperresource="com/john/hbatis/model/User.xml"/> </mappers> </configuration>
3.执行创建数据库和表的sql：
--Createthedatabasenamed'hbatis'.
--It'sOKtouse`,notOKtouse'or"surroundingthedatabasenametopreventitfrombeinginterpretedasakeywordifpossible.
CREATEDATABASEIFNOTEXISTS`hbatis`
DEFAULTCHARACTERSET=`UTF8`;
--Createatablenamed'User'
CREATETABLE`user`(
`id`int(11)NOTNULLAUTO_INCREMENT,
`name`varchar(50)DEFAULTNULL,
`age`int(11)DEFAULTNULL,
`address`varchar(200)DEFAULTNULL,
PRIMARYKEY(`id`)
)ENGINE=InnoDBAUTO_INCREMENT=2DEFAULTCHARSET=utf8;
--Insertatestrecord
InsertINTO`user`VALUES('1','john','120','hangzhou,westlake');
4.com.john.hbatis.model.User类：
publicclassUser{
privateintid;
privateStringname;
privateStringage;
privateStringaddress;
//Gettersandsettersareomitted
//如果有带参数的构造器，编译器不会自动生成无参构造器。当查询需要返回对象时，ORM框架用反射来调用对象的无参构造函数，导致异常：java.lang.NoSuchMethodException:com.john.hbatis.model.User.<init>()
//这时需要明确写出：
publicUser(){
}
publicUser(intid,Stringaddress){
this.id=id;
this.address=address;
}
publicUser(Stringname,intage,Stringaddress){
this.name=name;
this.age=age;
this.address=address;
}
}
com/john/hbatis/model路径下的User.xml
<?xmlversion="1.0"encoding="UTF-8"?>
<!DOCTYPEmapperPUBLIC"-//mybatis.org//DTDMapper3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mappernamespace="com.john.hbatis.model.UserMapper">
<selectid="getUserById"parameterType="int"resultType="User">
select*from`user`whereid=#{id}
</select>
</mapper>
5.测试类：
publicclassMyBatisBasicTest{
privatestaticfinalLoggerlog=LoggerFactory.getLogger(MyBatisBasicTest.class);
privatestaticSqlSessionFactorysqlSessionFactory;
privatestaticReaderreader;
@BeforeClass
publicstaticvoidinitial(){
try{
reader=Resources.getResourceAsReader("Configuration.xml");
sqlSessionFactory=newSqlSessionFactoryBuilder().build(reader);
}catch(IOExceptione){
log.error("Errorthrownwhilereadingtheconfiguration:{}",e);
}finally{
if(reader!=null){
try{
reader.close();
}catch(IOExceptione){
log.error("Errorthrownwhileclosingthereader:{}",e);
}
}
}
}
@Test
publicvoidqueryTest(){
SqlSessionsession=sqlSessionFactory.openSession();
Useruser=(User)session.selectOne("com.john.hbatis.model.UserMapper.getUserById",1);
log.info("{}:{}",user.getName(),user.getAddress());
}
}
以接口方式交互数据
上面的环境搭建是采用SqlSession的通用方法并强制转换的方式，存在着转换安全的问题：
Useruser=(User)session.selectOne("com.john.hbatis.model.UserMapper.getUserById",1);
可以采用接口加sql语句的方式来解决，sql语句理解为是接口的实现：
1.新建接口类：
packagecom.john.hbatis.mapper;
importcom.john.hbatis.model.User;
publicinterfaceIUserMapper{
UsergetUserById(intid);
}
2.修改User.xml文件，确保namespace属性值和接口的全限定名相同，且id属性值和接口方法名相同：
<mappernamespace="com.john.hbatis.mapper.IUserMapper"> <selectid="getUserById"
3.在MyBatisBasicTest类中添加测试方法：
@Test
publicvoidqueryInInterfaceWayTest(){
SqlSessionsession=sqlSessionFactory.openSession();
IUserMappermapper=session.getMapper(IUserMapper.class);//如果namespace和接口全限定名不一致，报org.apache.ibatis.binding.BindingException:Typeinterfacecom..IUserMapperisnotknowntotheMapperRegistry异常。
Useruser=mapper.getUserById(1);
log.info("{}:{}",user.getName(),user.getAddress());
}
附：
上面的实现是把sql语句放在XML文件中，并通过一定的约束来保证接口能够在XML中找到对应的SQL语句；
还有一种方式是通过接口+注解SQL方式来交互数据：
1.新建接口类：
packagecom.john.hbatis.mapper;
importorg.apache.ibatis.annotations.Select;
importcom.john.hbatis.model.User;
publicinterfaceIUserMapper2{
@Select({"select*from`user`whereid=#{id}"})
UsergetUserById(intid);
}
2.在Configuration.xml文件中加入：
<mappers> <mapperclass="com.john.hbatis.mapper.IUserMapper2"/> </mappers>
或在初始化语句中加入：
sqlSessionFactory.getConfiguration().addMapper(IUserMapper2.class);
3.相应修改上面的测试方法：
IUserMapper2mapper=session.getMapper(IUserMapper2.class);