MyBatis 注解开发的多表操作02 一对一查询 一对多查询 多对多查询 注解配置总结 需要的sql下载： 一对一 一对多 多对多 案例目录结构(一对一的)目录结构配置文件参考：Mybatis的基本使用注意：MyBatisConfig.xml配置文件里里替换成 <typeAliases> <!--<typeAlias type="com.limei.bean.Card" alias="card"/>--> <package name="com.itheima"/> </typeAliases>一对一查询一对一查询的需求：查询一个用户信息，与此同时查询出该用户对应的身份证信息Card实体类package com.limei.bean; public class Card { private Integer id; //主键id private String number; //身份证号 private Person p; //所属人的对象 public Card() { } public Card(Integer id, String number, Person p) { this.id = id; this.number = number; this.p = p; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getNumber() { return number; } public void setNumber(String number) { this.number = number; } public Person getP() { return p; } public void setP(Person p) { this.p = p; } @Override public String toString() { return "Card{" + "id=" + id + ", number='" + number + '\'' + ", p=" + p + '}'; } } Person实体类package com.limei.bean; public class Person { private Integer id; //主键id private String name; //人的姓名 private Integer age; //人的年龄 public Person() { } public Person(Integer id, String name, Integer age) { this.id = id; this.name = name; this.age = age; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } @Override public String toString() { return "Person{" + "id=" + id + ", name='" + name + '\'' + ", age=" + age + '}'; } } PersonMapper接口package com.limei.mapper; import com.limei.bean.Person; import org.apache.ibatis.annotations.Select; public interface PersonMapper { //根据id查询 @Select("SELECT * FROM person WHERE id=#{id}") public abstract Person selectById(Integer id); } CardMapper接口package com.limei.mapper; import com.limei.bean.Card; import com.limei.bean.Person; import org.apache.ibatis.annotations.One; import org.apache.ibatis.annotations.Result; import org.apache.ibatis.annotations.Results; import org.apache.ibatis.annotations.Select; import java.util.List; public interface CardMapper { //查询全部 @Select("SELECT * FROM card") @Results({ @Result(column = "id",property = "id"), @Result(column = "number",property = "number"), @Result( property = "p", // 被包含对象的变量名 javaType = Person.class, // 被包含对象的实际数据类型 column = "pid", // 根据查询出的card表中的pid字段来查询person表 /* one、@One 一对一固定写法 select属性：指定调用哪个接口中的哪个方法 */ one = @One(select = "com.limei.mapper.PersonMapper.selectById") ) }) public abstract List<Card> selectAll(); } Test01测试类package com.limei.test; import com.limei.bean.Card; import com.limei.mapper.CardMapper; 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.junit.Test; import java.io.InputStream; import java.util.List; public class Test01 { @Test public void selectAll() throws Exception{ //1.加载核心配置文件 InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(true); //4.获取CardMapper接口的实现类对象 CardMapper mapper = sqlSession.getMapper(CardMapper.class); //5.调用实现类对象中的方法，接收结果 List<Card> list = mapper.selectAll(); //6.处理结果 for (Card card : list) { System.out.println(card); } //7.释放资源 sqlSession.close(); is.close(); } } 一对多查询一对多查询的需求：查询一个班级，与此同时查询出该班级对应的学生信息Classes实体类package com.limei.bean; import java.util.List; public class Classes { private Integer id; //主键id private String name; //班级名称 private List<Student> students; //班级中所有学生对象 public Classes() { } public Classes(Integer id, String name, List<Student> students) { this.id = id; this.name = name; this.students = students; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<Student> getStudents() { return students; } public void setStudents(List<Student> students) { this.students = students; } @Override public String toString() { return "Classes{" + "id=" + id + ", name='" + name + '\'' + ", students=" + students + '}'; } } Student实体类package com.limei.bean; import java.util.List; public class Student { private Integer id; //主键id private String name; //学生姓名 private Integer age; //学生年龄 public Student() { } public Student(Integer id, String name, Integer age) { this.id = id; this.name = name; this.age = age; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } @Override public String toString() { return "Student{" + "id=" + id + ", name='" + name + '\'' + ", age=" + age + '}'; } } StudentMapper接口package com.limei.mapper; import com.limei.bean.Student; import org.apache.ibatis.annotations.Select; import java.util.List; public interface StudentMapper { //根据cid查询student表 @Select("SELECT * FROM student WHERE cid=#{cid}") public abstract List<Student> selectByCid(Integer cid); }ClassesMapper接口package com.limei.mapper; import com.limei.bean.Classes; import org.apache.ibatis.annotations.Many; import org.apache.ibatis.annotations.Result; import org.apache.ibatis.annotations.Results; import org.apache.ibatis.annotations.Select; import java.util.List; public interface ClassesMapper { //查询全部 @Select("SELECT * FROM classes") @Results({ @Result(column = "id",property = "id"), @Result(column = "name",property = "name"), @Result( property = "students", // 被包含对象的变量名 javaType = List.class, // 被包含对象的实际数据类型 column = "id", // 根据查询出的classes表的id字段来查询student表 /* many、@Many 一对多查询的固定写法 select属性：指定调用哪个接口中的哪个查询方法 */ many = @Many(select = "com.limei.mapper.StudentMapper.selectByCid") ) }) public abstract List<Classes> selectAll(); } Test01测试类package com.limei.test; import com.limei.bean.Classes; import com.limei.bean.Student; import com.limei.mapper.ClassesMapper; 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.junit.Test; import java.io.InputStream; import java.util.List; public class Test01 { @Test public void selectAll() throws Exception{ //1.加载核心配置文件 InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(true); //4.获取ClassesMapper接口的实现类对象 ClassesMapper mapper = sqlSession.getMapper( ClassesMapper.class); //5.调用实现类对象中的方法，接收结果 List<Classes> list = mapper.selectAll(); //6.处理结果 for (Classes cls : list) { System.out.println(cls.getId() + "," + cls.getName()); List<Student> students = cls.getStudents(); for (Student student : students) { System.out.println("\t" + student); } } //7.释放资源 sqlSession.close(); is.close(); } }多对多查询多对多查询的需求：查询学生以及所对应的课程信息Course实体类package com.limei.bean; public class Course { private Integer id; //主键id private String name; //课程名称 public Course() { } public Course(Integer id, String name) { this.id = id; this.name = name; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "Course{" + "id=" + id + ", name='" + name + '\'' + '}'; } } Student实体类package com.limei.bean; import java.util.List; public class Student { private Integer id; //主键id private String name; //学生姓名 private Integer age; //学生年龄 private List<Course> courses; //学生所选择的课程对象 public Student() { } public Student(Integer id, String name, Integer age, List<Course> courses) { this.id = id; this.name = name; this.age = age; this.courses = courses; } public List<Course> getCourses() { return courses; } public void setCourses(List<Course> courses) { this.courses = courses; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } @Override public String toString() { return "Student{" + "id=" + id + ", name='" + name + '\'' + ", age=" + age + '}'; } }CourseMapper接口package com.limei.mapper; import com.limei.bean.Course; import org.apache.ibatis.annotations.Select; import java.util.List; public interface CourseMapper { //根据学生id查询所选课程 @Select("SELECT c.id,c.name FROM stu_cr sc,course c WHERE sc.cid=c.id AND sc.sid=#{id}") public abstract List<Course> selectBySid(Integer id); }StudentMapper接口package com.limei.mapper; import com.limei.bean.Student; import org.apache.ibatis.annotations.Many; import org.apache.ibatis.annotations.Result; import org.apache.ibatis.annotations.Results; import org.apache.ibatis.annotations.Select; import java.util.List; public interface StudentMapper { //查询全部 @Select("SELECT DISTINCT s.id,s.name,s.age FROM student s,stu_cr sc WHERE sc.sid=s.id") @Results({ @Result(column = "id",property = "id"), @Result(column = "name",property = "name"), @Result(column = "age",property = "age"), @Result( property = "courses", // 被包含对象的变量名 javaType = List.class, // 被包含对象的实际数据类型 column = "id", // 根据查询出student表的id来作为关联条件，去查询中间表和课程表 /* many、@Many 一对多查询的固定写法 select属性：指定调用哪个接口中的哪个查询方法 */ many = @Many(select = "com.limei.mapper.CourseMapper.selectBySid") ) }) public abstract List<Student> selectAll(); }Test01测试类package com.limei.test; import com.limei.bean.Course; import com.limei.bean.Student; import com.limei.mapper.StudentMapper; 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.junit.Test; import java.io.InputStream; import java.util.List; public class Test01 { @Test public void selectAll() throws Exception{ //1.加载核心配置文件 InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper( StudentMapper.class); //5.调用实现类对象中的方法，接收结果 List<Student> list = mapper.selectAll(); //6.处理结果 for (Student student : list) { System.out.println(student.getId() + "," + student.getName() + "," + student.getAge()); List<Course> courses = student.getCourses(); for (Course cours : courses) { System.out.println("\t" + cours); } } //7.释放资源 sqlSession.close(); is.close(); } }配置总结@Results：封装映射关系的父注解。 Result[] value()：定义了 Result 数组 @Result：封装映射关系的子注解。 column 属性：查询出的表中字段名称 property 属性：实体对象中的属性名称 javaType 属性：被包含对象的数据类型 one 属性：一对一查询固定属性 @One：一对一查询的注解。 select 属性：指定调用某个接口中的方法 @Many：一对多查询的注解。 select 属性：指定调用某个接口中的方法

Mybatis 增删改查的注解方式01 MyBatis的常用注解 MyBatis的增删改查 注解开发总结 MyBatis的常用注解@Insert：实现新增@Update：实现更新@Delete：实现删除@Select：实现查询@Result：实现结果集封装@Results：可以与@Result 一起使用，封装多个结果集@One：实现一对一结果集封装@Many：实现一对多结果集封装MyBatis的增删改查注意：数据表以及各种配置参考Mybatis的基本使用案例目录结构MyBatisConfig.xml核心配置<?xml version="1.0" encoding="UTF-8" ?> <!--MyBatis的DTD约束--> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <!--configuration 核心根标签--> <configuration> <!--引入数据库连接的配置文件--> <properties resource="jdbc.properties"/> <!--配置LOG4J--> <settings> <setting name="logImpl" value="log4j"/> </settings> <!--起别名--> <typeAliases> <typeAlias type="com.limei.bean.Student" alias="student"/> <!--<package name="com.itheima.bean"/>--> </typeAliases> <!--environments配置数据库环境，环境可以有多个。default属性指定使用的是哪个--> <environments default="mysql"> <!--environment配置数据库环境 id属性唯一标识--> <environment id="mysql"> <!-- transactionManager事务管理。 type属性，采用JDBC默认的事务--> <transactionManager type="JDBC"></transactionManager> <!-- dataSource数据源信息 type属性 连接池--> <dataSource type="POOLED"> <!-- property获取数据库连接的配置信息 --> <property name="driver" value="${driver}" /> <property name="url" value="${url}" /> <property name="username" value="${username}" /> <property name="password" value="${password}" /> </dataSource> </environment> </environments> <!-- mappers引入映射配置文件 --> <mappers> <!--扫描使用注解的类所在的包--> <package name="com.limei.mapper"></package> </mappers> </configuration>StudentMapper接口//查询全部 @Select("SELECT * FROM student") public abstract List<Student> selectAll(); //新增数据 @Insert(" INSERT INTO student VALUES (#{id},#{name},#{birthday},#{address})") public abstract Integer insert(Student stu); //修改数据 @Update(" UPDATE student SET name = #{name},birthday = #{birthday},address=#{address} WHERE id = #{id}") public abstract Integer update(Student stu); //删除数据 @Delete("DELETE FROM student WHERE id = #{id}") public abstract Integer delete(String id); Test01测试类，查询所有public class Test01 { //String类型转换为Date类型 public Date conversionDate(String s){ String str =s; Date date=null; SimpleDateFormat sdf=null; try { sdf = new SimpleDateFormat ( "yyyy-MM-dd" ); date = sdf.parse ( str ); } catch (ParseException e) { e.printStackTrace (); } return date; } //查询所有 @Test public void selectAll() throws Exception{ //1.加载核心配置文件 InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder ().build(is); //3.通过工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper ( StudentMapper.class ); //5.调用实现类对象中的方法，接收结果 List<Student> list = mapper.selectAll (); //6.处理结果 for (Student student: list) { System.out.println(student); } //7.释放资源 sqlSession.close(); is.close(); } }添加操作，只需要改第五步，第六步遍历删除： Date date = conversionDate ( "1998-09-01" ); Student student=new Student ( "10010","张三",date,"北京市" ); Integer insert = mapper.insert ( student );更改操作，只需要改第五步，第六步遍历删除： Date date = conversionDate ( "1998-09-01" ); Student student=new Student ( "10010","李四",date,"北京市" ); Integer update = mapper.update ( student );删除操作，只需要改第五步，第六步遍历删除： Date date = conversionDate ( "1998-09-01" ); Integer delete = mapper.delete ( "10010" );注解开发总结注解可以简化开发操作，省略映射配置文件的编写。常用注解 @Select(“查询的 SQL 语句”)：执行查询操作注解@Insert(“查询的 SQL 语句”)：执行新增操作注解@Update(“查询的 SQL 语句”)：执行修改操作注解@Delete(“查询的 SQL 语句”)：执行删除操作注解配置映射关系<mappers> <package name="接口所在包"/> </mappers>

MyBatis的多表操作 一对一 一对多 多对多 一对一步骤一: sql语句准备CREATE TABLE person( id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20), age INT ); INSERT INTO person VALUES (NULL,'张三',26); INSERT INTO person VALUES (NULL,'李四',36); INSERT INTO person VALUES (NULL,'王五',28); CREATE TABLE card( id INT PRIMARY KEY AUTO_INCREMENT, number VARCHAR(30), pid INT, CONSTRAINT cp_fk FOREIGN KEY (pid) REFERENCES person(id) ); INSERT INTO card VALUES (NULL,'12345',1); INSERT INTO card VALUES (NULL,'23456',2); INSERT INTO card VALUES (NULL,'34567',3);步骤二:配置文件<?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.itheima.table01.OneToOneMapper"> <!--配置字段和实体对象属性的映射关系--> <resultMap id="oneToOne" type="card"> <id column="cid" property="id" /> <result column="number" property="number" /> <!-- association：配置被包含对象的映射关系 property：被包含对象的变量名 javaType：被包含对象的数据类型 --> <association property="p" javaType="person"> <id column="pid" property="id" /> <result column="name" property="name" /> <result column="age" property="age" /> </association> </resultMap> <select id="selectAll" resultMap="oneToOne"> SELECT c.id cid,number,pid,NAME,age FROM card c,person p WHERE c.pid=p.id </select> </mapper>步骤三：测试类 @Test public void selectAll() throws Exception{ //1.加载核心配置文件 InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(true); //4.获取OneToOneMapper接口的实现类对象 OneToOneMapper mapper = sqlSession.getMapper(OneToOneMapper.class); //5.调用实现类的方法，接收结果 List<Card> list = mapper.selectAll(); //6.处理结果 for (Card c : list) { System.out.println(c); } //7.释放资源 sqlSession.close(); is.close(); }3.一对一配置总结:<resultMap>：配置字段和对象属性的映射关系标签。 id 属性：唯一标识 type 属性：实体对象类型 <id>：配置主键映射关系标签。 <result>：配置非主键映射关系标签。 column 属性：表中字段名称 property 属性： 实体对象变量名称 <association>：配置被包含对象的映射关系标签。 property 属性：被包含对象的变量名 javaType 属性：被包含对象的数据类型一对多一对多模型： 一对多模型：班级和学生，一个班级可以有多个学生。代码实现步骤一: sql语句准备CREATE TABLE classes( id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20) ); INSERT INTO classes VALUES (NULL,'网课一班'); INSERT INTO classes VALUES (NULL,'网课二班'); CREATE TABLE student( id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(30), age INT, cid INT, CONSTRAINT cs_fk FOREIGN KEY (cid) REFERENCES classes(id) ); INSERT INTO student VALUES (NULL,'张三',23,1); INSERT INTO student VALUES (NULL,'李四',24,1); INSERT INTO student VALUES (NULL,'王五',25,2); INSERT INTO student VALUES (NULL,'赵六',26,2);步骤二:配置文件<mapper namespace="com.itheima.table02.OneToManyMapper"> <resultMap id="oneToMany" type="classes"> <id column="cid" property="id"/> <result column="cname" property="name"/> <!-- collection：配置被包含的集合对象映射关系 property：被包含对象的变量名 ofType：被包含对象的实际数据类型 --> <collection property="students" ofType="student"> <id column="sid" property="id"/> <result column="sname" property="name"/> <result column="sage" property="age"/> </collection> </resultMap> <select id="selectAll" resultMap="oneToMany"> SELECT c.id cid,c.name cname,s.id sid,s.name sname,s.age sage FROM classes c,student s WHERE c.id=s.cid </select> </mapper>步骤三：测试类 @Test public void selectAll() throws Exception{ //1.加载核心配置文件 InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(true); //4.获取OneToManyMapper接口的实现类对象 OneToManyMapper mapper = sqlSession.getMapper(OneToManyMapper.class); //5.调用实现类的方法，接收结果 List<Classes> classes = mapper.selectAll(); //6.处理结果 for (Classes cls : classes) { System.out.println(cls.getId() + "," + cls.getName()); List<Student> students = cls.getStudents(); for (Student student : students) { System.out.println("\t" + student); } } //7.释放资源 sqlSession.close(); is.close(); }多对多多表模型多对多操作多对多模型：学生和课程，一个学生可以选择多门课程、一个课程也可以被多个学生所选择。代码实现步骤一: sql语句准备CREATE TABLE course( id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20) ); INSERT INTO course VALUES (NULL,'数学'); INSERT INTO course VALUES (NULL,'英语'); CREATE TABLE stu_cr( id INT PRIMARY KEY AUTO_INCREMENT, sid INT, cid INT, CONSTRAINT sc_fk1 FOREIGN KEY (sid) REFERENCES student(id), CONSTRAINT sc_fk2 FOREIGN KEY (cid) REFERENCES course(id) ); INSERT INTO stu_cr VALUES (NULL,1,1); INSERT INTO stu_cr VALUES (NULL,1,2); INSERT INTO stu_cr VALUES (NULL,2,1); INSERT INTO stu_cr VALUES (NULL,2,2);步骤二:配置文件<?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.itheima.table03.ManyToManyMapper"> <resultMap id="manyToMany" type="student"> <id column="sid" property="id"/> <result column="sname" property="name"/> <result column="sage" property="age"/> <collection property="courses" ofType="course"> <id column="cid" property="id"/> <result column="cname" property="name"/> </collection> </resultMap> <select id="selectAll" resultMap="manyToMany"> SELECT sc.sid,s.name sname,s.age sage,sc.cid,c.name cname FROM student s,course c,stu_cr sc WHERE sc.sid=s.id AND sc.cid=c.id </select> </mapper>步骤三：测试类 @Test public void selectAll() throws Exception{ //1.加载核心配置文件 InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(true); //4.获取ManyToManyMapper接口的实现类对象 ManyToManyMapper mapper = sqlSession.getMapper(ManyToManyMapper.class); //5.调用实现类的方法，接收结果 List<Student> students = mapper.selectAll(); //6.处理结果 for (Student student : students) { System.out.println(student.getId() + "," + student.getName() + "," + student.getAge()); List<Course> courses = student.getCourses(); for (Course cours : courses) { System.out.println("\t" + cours); } } //7.释放资源 sqlSession.close(); is.close(); } 多表模型操作总结 <resultMap>：配置字段和对象属性的映射关系标签。 id 属性：唯一标识 type 属性：实体对象类型 <id>：配置主键映射关系标签。 <result>：配置非主键映射关系标签。 column 属性：表中字段名称 property 属性： 实体对象变量名称 <association>：配置被包含对象的映射关系标签。 property 属性：被包含对象的变量名 javaType 属性：被包含对象的数据类型 <collection>：配置被包含集合对象的映射关系标签。 property 属性：被包含集合对象的变量名 ofType 属性：集合中保存的对象数据类型

Mybatis代理方式的增删改查 代理开发方式介绍 增删改查的实现 总结 代理开发方式介绍采用 Mybatis 的代理开发方式实现 DAO 层的开发，这种方式是我们后面进入企业的主流。Mapper 接口开发方法只需要程序员编写Mapper 接口（相当于Dao 接口），由Mybatis 框架根据接口定义创建接口的动态代理对象，代理对象的方法体同上边Dao接口实现类方法。Mapper 接口开发需要遵循以下规范：1) Mapper.xml文件中的namespace与mapper接口的全限定名相同2) Mapper接口方法名和Mapper.xml中定义的每个statement的id相同3) Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql的parameterType的类型相同4) Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同增删改查的实现*** 案例目录结构 *** 该案例和《Mybatis的基本使用》使用的是同一个数据库以及实体类 1.编写StudentController类 2.编写StudentMapper接口 3.编写StudentService接口 4.编写StudentServiceImpl类 5.编写StudentMapper.xml文件 编写StudentController类 package com.limei.controller; import com.limei.bean.Student; import com.limei.service.StudentService; import com.limei.service.impl.StudentServiceImpl; import org.junit.Test; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Date; import java.util.List; /* 控制层测试类 */ public class StudentController { //创建业务层对象 private StudentService service = new StudentServiceImpl (); //String类型转换为Date类型 public Date conversionDate(String s){ String str =s; Date date=null; SimpleDateFormat sdf=null; try { sdf = new SimpleDateFormat ( "yyyy-MM-dd" ); date = sdf.parse ( str ); } catch (ParseException e) { e.printStackTrace (); } return date; } //查询全部功能测试 @Test public void selectAll() { List<Student> students = service.selectAll(); for (Student stu : students) { System.out.println(stu); } } //根据id查询功能测试 @Test public void selectById() { Student stu = service.selectById("10001"); System.out.println(stu); } //新增功能测试 @Test public void insert() { Date date = conversionDate ( "2011-09-01" ); Student stu = new Student("10010","赵六",date,"上海市"); Integer result = service.insert(stu); System.out.println(result); } //修改功能测试 @Test public void update() { Date date = conversionDate ( "2011-09-01" ); Student stu = new Student("10010","赵五",date,"上海市"); Integer result = service.update(stu); System.out.println(result); } //删除功能测试 @Test public void delete() { Integer result = service.delete("10010"); System.out.println(result); } // 多条件查询 @Test public void selectCondition(){ Student stu = new Student(); stu.setId("10002"); stu.setName("李四"); List<Student> list = service.selectCondition ( stu ); //6.处理结果 for (Student student : list) { System.out.println(student); } } //根据多个id查询 @Test public void selectByIds(){ List<String> ids = new ArrayList<> (); ids.add("10001"); ids.add("10002"); ids.add("10003"); List<Student> list = service.selectByIds ( ids ); for (Student student:list){ System.out.println (student); } } } 编写StudentMapper接口package com.limei.mapper; import com.limei.bean.Student; import java.util.List; public interface StudentMapper { //查询全部 public abstract List<Student> selectAll(); //根据id查询 public abstract Student selectById(String id); //新增数据 public abstract Integer insert(Student stu); //修改数据 public abstract Integer update(Student stu); //删除数据 public abstract Integer delete(String id); //多条件查询 public abstract List<Student> selectCondition(Student stu); //根据多个id查询 public abstract List<Student> selectByIds(List<String> ids); } 编写StudentService接口package com.limei.service; import com.limei.bean.Student; import java.util.List; /* 业务层接口 */ public interface StudentService { //查询全部 public abstract List<Student> selectAll(); //根据id查询 public abstract Student selectById(String id); //新增数据 public abstract Integer insert(Student stu); //修改数据 public abstract Integer update(Student stu); //删除数据 public abstract Integer delete(String id); //多条件查询 public abstract List<Student> selectCondition(Student stu); //根据多个id查询 public abstract List<Student> selectByIds(List<String> ids); } 编写StudentServiceImpl类package com.limei.service.impl; import com.limei.bean.Student; import com.limei.mapper.StudentMapper; import com.limei.service.StudentService; 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 java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.List; /* 业务层实现类 */ public class StudentServiceImpl implements StudentService { //查询全部 @Override public List<Student> selectAll() { List<Student> list = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); System.out.println (is); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 list = mapper.selectAll(); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return list; } @Override public Student selectById(String id) { Student stu = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 stu = mapper.selectById(id); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return stu; } @Override public Integer insert(Student stu) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.insert(stu); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } @Override public Integer update(Student stu) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.update(stu); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } @Override public Integer delete(String id) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.delete(id); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } //多条件查询 @Override public List<Student> selectCondition(Student stu) { List<Student> list=null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 list = mapper.selectCondition ( stu ); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return list; } //根据多个id查询 @Override public List<Student> selectByIds(List<String> ids) { List<Student> list = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 list = mapper.selectByIds ( ids ); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return list; } } 编写StudentMapper.xml文件<?xml version="1.0" encoding="UTF-8" ?> <!--MyBatis的DTD约束--> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!-- mapper：核心根标签 namespace属性：名称空间 --> <mapper namespace="com.limei.mapper.StudentMapper"> <!-- select：查询功能的标签 id属性：唯一标识 resultType属性：指定结果映射对象类型 parameterType属性：指定参数映射对象类型 --> <select id="selectAll" resultType="student"> SELECT * FROM student </select> <select id="selectById" resultType="student" parameterType="String"> SELECT * FROM student WHERE id = #{id} </select> <insert id="insert" parameterType="student"> INSERT INTO student VALUES (#{id},#{name},#{birthday},#{address}) </insert> <update id="update" parameterType="student"> UPDATE student SET name = #{name},birthday = #{birthday},address=#{address} WHERE id = #{id} </update> <delete id="delete" parameterType="String"> DELETE FROM student WHERE id = #{id} </delete> <!-- <where>：条件标签。如果有动态条件，则使用该标签代替 where 关键字。 <if>：条件判断标签。 <if test=“条件判断”> 查询条件拼接 </if> --> <select id="selectCondition" resultType="student" parameterType="student"> SELECT * FROM student <where> <if test="id != null"> id = #{id} </if> <if test="name != null"> AND name = #{name} </if> </where> </select> <!-- 属性 collection：参数容器类型， (list-集合， array-数组)。 open：开始的 SQL 语句。 close：结束的 SQL 语句。 item：参数变量名。 separator：分隔符。 --> <select id="selectByIds" resultType="student" parameterType="list"> SELECT * FROM student <where> <foreach collection="list" open="id IN (" close=")" item="id" separator=","> #{id} </foreach> </where> </select> </mapper> 总结此目录缺失的文件去Mybatis的基本使用中去寻找接口代理方式可以让我们只编写接口即可，而实现类对象由 MyBatis 生成。 实现规则 ：映射配置文件中的名称空间必须和 Dao 层接口的全类名相同。映射配置文件中的增删改查标签的 id 属性必须和 Dao 层接口的方法名相同。映射配置文件中的增删改查标签的 parameterType 属性必须和 Dao 层接口方法的参数相同。映射配置文件中的增删改查标签的 resultType 属性必须和 Dao 层接口方法的返回值相同。 获取动态代理对象 SqlSession 功能类中的 getMapper() 方法。

Mybatis的基本使用 什么是Mybatis Mybatis的搭建步骤 什么是Mybatis mybatis 是一个优秀的基于java的持久层框架，它内部封装了jdbc，使开发者只需要关注sql语句本身，而不需要花费精力去处理加载驱动、创建连接、创建statement等繁杂的过程。mybatis通过xml或注解的方式将要执行的各种 statement配置起来，并通过java对象和statement中sql的动态参数进行映射生成最终执行的sql语句。最后mybatis框架执行sql并将结果映射为java对象并返回。采用ORM思想解决了实体和数据库映射的问题，对jdbc 进行了封装，屏蔽了jdbc api 底层访问细节，使我们不用与jdbc api 打交道，就可以完成对数据库的持久化操作。MyBatis官网地址：http://www.mybatis.org/mybatis-3/ Mybatis的搭建步骤MyBatis开发步骤： ①添加MyBatis的jar包 ②创建Student数据表 ③编写Studentr实体类 ④编写映射文件StudentMapper.xml ⑤编写核心文件MyBatisConfig.xml ⑥编写测试类*** 测试案例目录结构 *** jdbc.properties 编写Studentr实体类 package com.limei.bean; import java.util.Date; public class Student { private String id; private String name; private Date birthday; private String address; public Student() { } public Student(String id, String name, Date birthday, String address) { this.id = id; this.name = name; this.birthday = birthday; this.address = address; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Override public String toString() { return "Student{" + "id='" + id + '\'' + ", name='" + name + '\'' + ", birthday=" + birthday + ", address='" + address + '\'' + '}'; } } ④编写映射文件StudentMapper.xml <?xml version="1.0" encoding="UTF-8" ?> <!--MyBatis的DTD约束--> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!-- mapper：核心根标签 namespace属性：名称空间 --> <mapper namespace="StudentMapper"> <!-- select：查询功能的标签 id属性：唯一标识 resultType属性：指定结果映射对象类型 parameterType属性：指定参数映射对象类型 --> <select id="selectAll" resultType="student"> SELECT * FROM student </select> <update id="update" parameterType="student"> UPDATE student SET name = #{name},birthday = #{birthday},address=#{address} WHERE id = #{id} </update> </mapper> ⑤编写核心文件MyBatisConfig.xml <?xml version="1.0" encoding="UTF-8" ?> <!--MyBatis的DTD约束--> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <!--configuration 核心根标签--> <configuration> <!--引入数据库连接的配置文件--> <properties resource="jdbc.properties"/> <!--配置LOG4J--> <settings> <setting name="logImpl" value="log4j"/> </settings> <!--起别名--> <typeAliases> <typeAlias type="com.limei.bean.Student" alias="student"/> <!--<package name="com.limei.bean"/>--> </typeAliases> <!--environments配置数据库环境，环境可以有多个。default属性指定使用的是哪个--> <environments default="mysql"> <!--environment配置数据库环境 id属性唯一标识--> <environment id="mysql"> <!-- transactionManager事务管理。 type属性，采用JDBC默认的事务--> <transactionManager type="JDBC"></transactionManager> <!-- dataSource数据源信息 type属性 连接池--> <dataSource type="POOLED"> <!-- property获取数据库连接的配置信息 --> <property name="driver" value="${driver}" /> <property name="url" value="${url}" /> <property name="username" value="${username}" /> <property name="password" value="${password}" /> </dataSource> </environment> </environments> <!-- mappers引入映射配置文件 --> <mappers> <!-- mapper 引入指定的映射配置文件 resource属性指定映射配置文件的名称 --> <mapper resource="StudentMapper.xml"/> </mappers> </configuration> 编写测试类 package com.limei.dao; import com.limei.bean.Student; 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.junit.Test; import java.io.InputStream; import java.util.List; public class StudentTest01 { /* 查询全部 */ @Test public void selectAll() throws Exception{ //1.加载核心配置文件 //InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); InputStream is = StudentTest01.class.getClassLoader().getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过SqlSession工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(); //4.执行映射配置文件中的sql语句，并接收结果 List<Student> list = sqlSession.selectList("StudentMapper.selectAll"); //5.处理结果 for (Student stu : list) { System.out.println(stu); } //6.释放资源 sqlSession.close(); is.close(); } /* 修改功能 */ @Test public void update() throws Exception{ //1.加载核心配置文件 InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(); //SqlSession sqlSession = sqlSessionFactory.openSession(true);为自动提交事务 //String类型转换为Date类型 String str ="2000-02-26"; SimpleDateFormat sdf = new SimpleDateFormat ( "yyyy-MM-dd" ); Date date = sdf.parse ( str ); //4.执行映射配置文件中的sql语句，并接收结 Student stu = new Student("10001","阿画",date,"河南省周口市"); int result = sqlSession.update("StudentMapper.update",stu); //5.提交事务 sqlSession.commit(true); //6.处理结果 System.out.println(result); //7.释放资源 sqlSession.close(); is.close(); } } 查询结果