1. 步骤：
- (1). 加包
- (2). 编写db.properties；编写conf.xml，将db.properties加入到conf.xml；引入别名
- (3). 建立实体类
- (4). 编写sql操作对应的***Mapper.xml文件
- (5). 将sql操作对应的***Mapper.xml文件注册到conf.xml文件中
- (6). 编写MyBaitsUtils
- (7). 测试
2. 详细步骤
- (1). 加包
- (2). 编写db.properties；
driverClass=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/mybatis1 username=root password=lfdy
- 编写conf.xml，将db.properties加入到conf.xml；
<!-- 加载db.properties 这段必须放在上面--><properties resource="db.properties"></properties><!-- 配置连接数据库信息 --><environments default="development"><environment id="development"><transactionManager type="JDBC" /><dataSource type="POOLED"><property name="driver" value="${driverClass}"/><property name="url" value="${url}"/><property name="username" value="${username}"/><property name="password" value="${password}"/></dataSource></environment></environments>- 引入别名
<!-- 加入别名 --><typeAliases><package name="com.atguigu.mybatis.domain"/></typeAliases>- (3). 建立实体类
package com.atguigu.mybatis.domain;import java.util.List;/*** @author hp**/ public class Classes {private int id;private String name;private Teacher teacher;private List<Student> students;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Teacher getTeacher() {return teacher;}public void setTeacher(Teacher teacher) {this.teacher = teacher;}public List<Student> getStudents() {return students;}public void setStudents(List<Student> students) {this.students = students;}public Classes(int id, String name, Teacher teacher, List<Student> students) {super();this.id = id;this.name = name;this.teacher = teacher;this.students = students;}public Classes() {super();}@Overridepublic String toString() {return "Classses [id=" + id + ", name=" + name + ", teacher=" + teacher + ", students=" + students + "]";}}
package com.atguigu.mybatis.domain;/*** @author hp**/ public class Teacher {private int id;private String name;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Teacher(int id, String name) {super();this.id = id;this.name = name;}public Teacher() {super();}@Overridepublic String toString() {return "Teacher [id=" + id + ", name=" + name + "]";}}
package com.atguigu.mybatis.domain;/*** @author hp**/ public class Student {private int id;private String name;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Student(int id, String name) {super();this.id = id;this.name = name;}public Student() {super();}@Overridepublic String toString() {return "Student [id=" + id + ", name=" + name + "]";}}
- (4). 编写sql操作对应的***Mapper.xml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.atguigu.mybatis.mapper.ClassMapper">
<!-- 方式1：嵌套结果 --><select id="getClass" parameterType="int" resultMap="ClassResultMap3">select * from class c,teacher t,student s where c.teacher_id = t.t_id and c.c_id = s.class_id and c.c_id = #{id}</select><resultMap type="Classes" id="ClassResultMap3"><id property="id" column="c_id"/><result property="name" column="c_name"/><association property="teacher" column="teacher_id" javaType="Teacher"><id property="id" column="t_id"/><result property="name" column="t_name"/></association><collection property="students" ofType="Student"><id property="id" column="s_id"/><result property="name" column="s_name"/></collection></resultMap>
<!-- 嵌套chaxun查询 -->
<select id="getClass2" parameterType="int" resultMap="ClassResultMap2">
select * from class where c_id = #{id}
</select>
<resultMap type="Classes" id="ClassResultMap2">
<id property="id" column="c_id"/>
<result property="name" column="c_name"/>
<association property="teacher" column="teacher_id" javaType="Teacher" select="getTeacher2"/>
<collection property="students" column="c_id" ofType="Student" select="getStudent2"/>
</resultMap>
<select id="getTeacher2" parameterType="int" resultType="Teacher">
select t_id id,t_name name from teacher where t_id=#{id}
</select>
<select id="getStudent2" parameterType="int" resultType="Student">
select s_id id,s_name name from student where class_id=#{id}
</select>
</mapper>
- (5). 将sql操作对应的***Mapper.xml文件注册到conf.xml文件中
<!-- 注册sql映射的mapper文件 --><mappers><mapper resource="com/atguigu/mybatis/mapper/ClassMapper.xml" /></mappers>
- (6). 编写MyBaitsUtils
package com.atguigu.mybatis.test;import java.io.InputStream;import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder;public class MyBatisUtils {public static SqlSessionFactory getFactory(){String resource = "config.xml";InputStream is = MyBatisUtils.class.getClassLoader().getResourceAsStream(resource);SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);return factory;}}
- (7). 测试
package com.atguigu.mybatis.test;import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import com.atguigu.mybatis.domain.*;/*** @author hp**/ public class MyBatisTest {public static void main(String[] args) {SqlSessionFactory factory = MyBatisUtils.getFactory();SqlSession session = factory.openSession();String statement = "com.atguigu.mybatis.mapper.ClassMapper.getClass";Classes c= (Classes) session.selectOne(statement,1);System.out.println(c);session.close();}}
