#{sql}:动态参数
${sql}:直接拼接到sql语句里面
输入不存在字段的时候:
#{sql}不会报错
${sql}报错
#{sql}
2017-11-10 09:44:50 DEBUG com.qf.dao.IUserDao.getUserById:142 - ==> Preparing: select ? from t_user where id = ?
2017-11-10 09:44:50 DEBUG com.qf.dao.IUserDao.getUserById:142 - ==> Parameters: id,name(String), 3(Integer)
${sql}
2017-11-10 09:45:37 DEBUG com.qf.dao.IUserDao.getUserById:142 - ==> Preparing: select id,name from t_user where id = ?
2017-11-10 09:45:37 DEBUG com.qf.dao.IUserDao.getUserById:142 - ==> Parameters: 3(Integer)
0.数据库
1.创建项目
2.建包建配置文件
com.qf.entity
com.qf.dao
com.qf.mapper
com.qf.utils
mybatis-config.xml
3.con.qf.entity包中创建实体类
package com.qf.entity; public class User { private Integer id; private String name; private String password; private String isAdmin; public User(String name, String password) { this.name = name; this.password = password; } public User() { } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getIsAdmin() { return isAdmin; } public void setIsAdmin(String isAdmin) { this.isAdmin = isAdmin; } @Override public String toString() { return "User [id=" + id + ", name=" + name + ", password=" + password + ", isAdmin=" + isAdmin + "]"; } }
4.con.qf.dao包中创建接口
package com.qf.dao; import org.apache.ibatis.annotations.Param; import com.qf.entity.User; public interface IUserDao { public User getUserById(@Param("sql")String sql,@Param("id")Integer id); }
5.配置jdbc.properties配置文件
jdbc.url =jdbc:mysql://localhost:3306/1707_hibernate jdbc.name=root jdbc.password=root jdbc.driver=com.mysql.jdbc.Driver
配置mybatis-config.xml配置文件
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <!-- 加载属性文件 resource:本地资源文件 --> <properties resource="jdbc.properties"></properties> <typeAliases> <package name="com.qf.entity"/> </typeAliases> <environments default="development"> <environment id="development"> <transactionManager type="JDBC" /> <dataSource type="POOLED"> <property name="driver" value="${jdbc.driver}" /> <property name="url" value="${jdbc.url}" /> <property name="username" value="${jdbc.name}" /> <property name="password" value="${jdbc.password}" /> </dataSource> </environment> </environments> </configuration>
6.com.qf.mapper包创建接口的映射文件
<?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.qf.dao.IUserDao"> <!-- #{sql}:动态参数 ${sql}:直接拼接到sql语句里面 --> <select id="getUserById" resultType="user"> select #{sql} from t_user where id = #{id} </select> </mapper>
7.在mybatis-config.xml里面读取Mapper文件
<!-- Mapper文件 --> <mappers> <mapper resource="com/qf/mapper/IUserDao.xml" /> </mappers>
8.com.qf.util工具类
package com.qf.utils; import java.io.IOException; import java.io.InputStream; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.xml.sax.InputSource; public class MyBatisUtil { private static SqlSessionFactory sqlSessionFactory; public static SqlSessionFactory getSqlSessionFactory() { if (sqlSessionFactory == null) { initSqlSessionFactory(); // 为空再去参加 } return sqlSessionFactory; } private static void initSqlSessionFactory() { InputStream ips = null; try { // 1.指定配置文件 ips = Resources.getResourceAsStream("mybatis-config.xml"); // 2.赋值操作 synchronized (MyBatisUtil.class) { if (sqlSessionFactory == null) { sqlSessionFactory = new SqlSessionFactoryBuilder().build(ips); } } } catch (IOException e) { e.printStackTrace(); } finally { if (ips != null) { try { ips.close(); } catch (IOException e) { e.printStackTrace(); } } } } }
9.测试类
package com.qf.dao; import java.util.HashMap; import java.util.Map; import org.apache.ibatis.session.SqlSession; import org.junit.Test; import com.qf.entity.User; import com.qf.utils.MyBatisUtil; public class UserDaoTest { @Test public void testGetUserById() { SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession(); IUserDao userDao = sqlSession.getMapper(IUserDao.class); User user = userDao.getUserById("id,name,passwordsdfasdfa", 3); System.out.println(user); sqlSession.commit(); sqlSession.close(); } }