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在数据库方面我们最常用的应该JDBC、Hibernate和Mybatis。通过JDBC方式连接数据库,我们会发现工作量是相当的复杂。我们得处理一些琐碎的关闭。然后入参出参我们都得自己管理。基于次产生了ORM(Object Relational Mapping)模型。
<dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.0</version> </dependency>
package com.github.zxhtom.mapper; import com.github.zxhtom.model.Student; import java.util.List; public interface StudentMapper { /** * 获取学生列表 * @return */ public List<Student> getStudents(); /** * 通过id获取学生信息 * @param id * @return */ public Student getStudentByStuId(String id); }
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" > <mapper namespace="com.github.zxhtom.mapper.StudentMapper"> <select id="getStudents" resultType="com.github.zxhtom.model.Student"> select * from student </select> <select id="getStudentByStuId" resultType="com.github.zxhtom.model.Student"> select * from student where id=#{id} </select> </mapper>
<?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> <!--引入外部配置文件--> <properties resource="config.properties"></properties> <!--定义别名--> <typeAliases> <package name=""/> </typeAliases> <!--定义数据库信息,默认使用development数据库构建环境--> <environments default="development"> <environment id="development"> <!--jdbc事物管理--> <transactionManager type="JDBC"></transactionManager> <!--配置数据库连接信息--> <dataSource type="POOLED"> <property name="driver" value="${database.driver}"/> <property name="url" value="${database.url}"/> <property name="username" value="${database.username}"/> <property name="password" value="${database.password}"/> </dataSource> </environment> </environments> <mappers> <mapper resource="com/github/zxhtom/mapper/StudentMapper.xml"></mapper> </mappers> </configuration>
//获取mybatis-config.xml位置 InputStream inputStream = Resources.getResourceAsStream(Constant.MYBATIS); //加载mybatis-config,并创建sqlsessionfactory对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //创建sqlsession对象 SqlSession sqlSession = sqlSessionFactory.openSession(); Map<String, Object> paramMap = new HashMap<>(); paramMap.put("id", 1); //执行select语句,将resultSet映射成对象并返回 StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class); List<Student> students = studentMapper.getStudents(); studentPrint(students);
Map<Object, Object> properties = PropertiesUtil.getProperties("config.properties"); PooledDataSource dataSource = new PooledDataSource(); dataSource.setDriver(properties.get("database.driver").toString()); dataSource.setUrl(properties.get("database.url").toString()); dataSource.setUsername(properties.get("database.username").toString()); dataSource.setPassword(properties.get("database.password").toString()); //构建数据库事物方式 TransactionFactory transactionFactory = new JdbcTransactionFactory(); //创建数据库运行环境 Environment environment = new Environment("development",transactionFactory,dataSource); //构建Configure对象 Configuration configuration = new Configuration(environment); //注册别名 configuration.getTypeAliasRegistry().registerAlias("stu", Student.class); //加入一个映射器 configuration.addMapper(StudentMapper.class); //使用sqlsessionfactoryBuilder构建sqlsessionfactory SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration); SqlSession sqlSession = sqlSessionFactory.openSession(); StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class); List<Student> students = studentMapper.getStudents(); studentPrint(students);
resultMap