本文以实例说明Mapper文件的标签的使用。
配置文件在【MyBatis】配置文件示例
DAO文件
DepartmentMapper.java
package com.atguigu.mybatis.dao;
import com.atguigu.mybatis.bean.Department;
public interface DepartmentMapper {
public Department getDeptById(Integer id);
public Department getDeptByIdPlus(Integer id);
public Department getDeptByIdStep(Integer id);
}
EmployeeMapper.java
package com.atguigu.mybatis.dao;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.annotations.MapKey;
import org.apache.ibatis.annotations.Param;
import com.atguigu.mybatis.bean.Employee;
public interface EmployeeMapper {
//多条记录封装一个map:Map<Integer,Employee>:键是这条记录的主键,值是记录封装后的javaBean
//@MapKey:告诉mybatis封装这个map的时候使用哪个属性作为map的key
@MapKey("lastName")
public Map<String, Employee> getEmpByLastNameLikeReturnMap(String lastName);
//返回一条记录的map;key就是列名,值就是对应的值
public Map<String, Object> getEmpByIdReturnMap(Integer id);
public List<Employee> getEmpsByLastNameLike(String lastName);
public Employee getEmpByMap(Map<String, Object> map);
public Employee getEmpByIdAndLastName(@Param("id")Integer id,@Param("lastName")String lastName);
public Employee getEmpById(Integer id);
public Long addEmp(Employee employee);
public boolean updateEmp(Employee employee);
public void deleteEmpById(Integer id);
}
EmployeeMapperPlus.java
package com.atguigu.mybatis.dao;
import java.util.List;
import com.atguigu.mybatis.bean.Employee;
public interface EmployeeMapperPlus {
public Employee getEmpById(Integer id);
public Employee getEmpAndDept(Integer id);
public Employee getEmpByIdStep(Integer id);
public List<Employee> getEmpsByDeptId(Integer deptId);
}
映射文件
DepartmentMapper.xml 结果集示例,分段查询
<?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.dao.DepartmentMapper">
<!--public Department getDeptById(Integer id); -->
<select id="getDeptById" resultType="com.atguigu.mybatis.bean.Department">
select id,dept_name departmentName from tbl_dept where id=#{id}
</select>
<!--
public class Department {
private Integer id;
private String departmentName;
private List<Employee> emps;
did dept_name || eid last_name email gender
-->
<!--嵌套结果集的方式,使用collection标签定义关联的集合类型的属性封装规则 -->
<resultMap type="com.atguigu.mybatis.bean.Department" id="MyDept">
<id column="did" property="id"/>
<result column="dept_name" property="departmentName"/>
<!--
collection定义关联集合类型的属性的封装规则
ofType:指定集合里面元素的类型
-->
<collection property="emps" ofType="com.atguigu.mybatis.bean.Employee">
<!-- 定义这个集合中元素的封装规则 -->
<id column="eid" property="id"/>
<result column="last_name" property="lastName"/>
<result column="email" property="email"/>
<result column="gender" property="gender"/>
</collection>
</resultMap>
<!-- public Department getDeptByIdPlus(Integer id); -->
<select id="getDeptByIdPlus" resultMap="MyDept">
SELECT d.id did,d.dept_name dept_name,
e.id eid,e.last_name last_name,e.email email,e.gender gender
FROM tbl_dept d
LEFT JOIN tbl_employee e
ON d.id=e.d_id
WHERE d.id=#{id}
</select>
<!-- collection:分段查询 -->
<resultMap type="com.atguigu.mybatis.bean.Department" id="MyDeptStep">
<id column="id" property="id"/>
<id column="dept_name" property="departmentName"/>
<collection property="emps"
select="com.atguigu.mybatis.dao.EmployeeMapperPlus.getEmpsByDeptId"
column="{deptId=id}" fetchType="lazy"></collection>
</resultMap>
<!-- public Department getDeptByIdStep(Integer id); -->
<select id="getDeptByIdStep" resultMap="MyDeptStep">
select id,dept_name from tbl_dept where id=#{id}
</select>
<!-- 扩展:多列的值传递过去:
将多列的值封装map传递;
column="{key1=column1,key2=column2}"
fetchType="lazy":表示使用延迟加载;
- lazy:延迟
- eager:立即
-->
</mapper>
EmployeeMapper.xml MySql和Oracle获取主键的方式
<?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.dao.EmployeeMapper">
<!--
namespace:名称空间;指定为接口的全类名
id:唯一标识
resultType:返回值类型
#{id}:从传递过来的参数中取出id值
public Employee getEmpById(Integer id);
-->
<!--public Map<Integer, Employee> getEmpByLastNameLikeReturnMap(String lastName); -->
<select id="getEmpByLastNameLikeReturnMap" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee where last_name like #{lastName}
</select>
<!--public Map<String, Object> getEmpByIdReturnMap(Integer id); -->
<select id="getEmpByIdReturnMap" resultType="map">
select * from tbl_employee where id=#{id}
</select>
<!-- public List<Employee> getEmpsByLastNameLike(String lastName); -->
<!--resultType:如果返回的是一个集合,要写集合中元素的类型 -->
<select id="getEmpsByLastNameLike" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee where last_name like #{lastName}
</select>
<!-- public Employee getEmpByMap(Map<String, Object> map); -->
<select id="getEmpByMap" resultType="com.atguigu.mybatis.bean.Employee">
select * from ${tableName} where id=${id} and last_name=#{lastName}
</select>
<!-- public Employee getEmpByIdAndLastName(Integer id,String lastName);-->
<select id="getEmpByIdAndLastName" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee where id = #{id} and last_name=#{lastName}
</select>
<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee where id = #{id}
</select>
<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee"
databaseId="mysql">
select * from tbl_employee where id = #{id}
</select>
<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee"
databaseId="oracle">
select EMPLOYEE_ID id,LAST_NAME lastName,EMAIL email
from employees where EMPLOYEE_ID=#{id}
</select>
<!-- public void addEmp(Employee employee); -->
<!-- parameterType:参数类型,可以省略,
获取自增主键的值:
mysql支持自增主键,自增主键值的获取,mybatis也是利用statement.getGenreatedKeys();
useGeneratedKeys="true";使用自增主键获取主键值策略
keyProperty;指定对应的主键属性,也就是mybatis获取到主键值以后,将这个值封装给javaBean的哪个属性
-->
<insert id="addEmp" parameterType="com.atguigu.mybatis.bean.Employee"
useGeneratedKeys="true" keyProperty="id" databaseId="mysql">
insert into tbl_employee(last_name,email,gender)
values(#{lastName},#{email},#{gender})
</insert>
<!--
获取非自增主键的值:
Oracle不支持自增;Oracle使用序列来模拟自增;
每次插入的数据的主键是从序列中拿到的值;如何获取到这个值;
-->
<insert id="addEmp" databaseId="oracle">
<!--
keyProperty:查出的主键值封装给javaBean的哪个属性
order="BEFORE":当前sql在插入sql之前运行
AFTER:当前sql在插入sql之后运行
resultType:查出的数据的返回值类型
BEFORE运行顺序:
先运行selectKey查询id的sql;查出id值封装给javaBean的id属性
在运行插入的sql;就可以取出id属性对应的值
AFTER运行顺序:
先运行插入的sql(从序列中取出新值作为id);
再运行selectKey查询id的sql;
-->
<selectKey keyProperty="id" order="BEFORE" resultType="Integer">
<!-- 编写查询主键的sql语句 -->
<!-- BEFORE-->
select EMPLOYEES_SEQ.nextval from dual
<!-- AFTER:
select EMPLOYEES_SEQ.currval from dual -->
</selectKey>
<!-- 插入时的主键是从序列中拿到的 -->
<!-- BEFORE:-->
insert into employees(EMPLOYEE_ID,LAST_NAME,EMAIL)
values(#{id},#{lastName},#{email<!-- ,jdbcType=NULL -->})
<!-- AFTER:
insert into employees(EMPLOYEE_ID,LAST_NAME,EMAIL)
values(employees_seq.nextval,#{lastName},#{email}) -->
</insert>
<!-- public void updateEmp(Employee employee); -->
<update id="updateEmp">
update tbl_employee
set last_name=#{lastName},email=#{email},gender=#{gender}
where id=#{id}
</update>
<!-- public void deleteEmpById(Integer id); -->
<delete id="deleteEmpById">
delete from tbl_employee where id=#{id}
</delete>
</mapper>
EmployeeMapperPlus.xml 结果集的封装:一对一,一对多,以及延迟加载和解释器的使用
<?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.dao.EmployeeMapperPlus">
<!--自定义某个javaBean的封装规则
type:自定义规则的Java类型
id:唯一id方便引用
-->
<resultMap type="com.atguigu.mybatis.bean.Employee" id="MySimpleEmp">
<!--指定主键列的封装规则
id定义主键会底层有优化;
column:指定哪一列
property:指定对应的javaBean属性
-->
<id column="id" property="id"/>
<!-- 定义普通列封装规则 -->
<result column="last_name" property="lastName"/>
<!-- 其他不指定的列会自动封装:我们只要写resultMap就把全部的映射规则都写上。 -->
<result column="email" property="email"/>
<result column="gender" property="gender"/>
</resultMap>
<!-- resultMap:自定义结果集映射规则; -->
<!-- public Employee getEmpById(Integer id); -->
<select id="getEmpById" resultMap="MySimpleEmp">
select * from tbl_employee where id=#{id}
</select>
<!--
场景一:
查询Employee的同时查询员工对应的部门
Employee===Department
一个员工有与之对应的部门信息;
id last_name gender d_id did dept_name (private Department dept;)
-->
<!--
联合查询:级联属性封装结果集
-->
<resultMap type="com.atguigu.mybatis.bean.Employee" id="MyDifEmp">
<id column="id" property="id"/>
<result column="last_name" property="lastName"/>
<result column="gender" property="gender"/>
<result column="did" property="dept.id"/>
<result column="dept_name" property="dept.departmentName"/>
</resultMap>
<!--
使用association定义关联的单个对象的封装规则;
-->
<resultMap type="com.atguigu.mybatis.bean.Employee" id="MyDifEmp2">
<id column="id" property="id"/>
<result column="last_name" property="lastName"/>
<result column="gender" property="gender"/>
<!-- association可以指定联合的javaBean对象
property="dept":指定哪个属性是联合的对象
javaType:指定这个属性对象的类型[不能省略]
-->
<association property="dept" javaType="com.atguigu.mybatis.bean.Department">
<id column="did" property="id"/>
<result column="dept_name" property="departmentName"/>
</association>
</resultMap>
<!-- public Employee getEmpAndDept(Integer id);-->
<select id="getEmpAndDept" resultMap="MyDifEmp">
SELECT e.id id,e.last_name last_name,e.gender gender,e.d_id d_id,
d.id did,d.dept_name dept_name FROM tbl_employee e,tbl_dept d
WHERE e.d_id=d.id AND e.id=#{id}
</select>
<!-- 使用association进行分步查询:
1、先按照员工id查询员工信息
2、根据查询员工信息中的d_id值去部门表查出部门信息
3、部门设置到员工中;
-->
<!-- id last_name email gender d_id -->
<resultMap type="com.atguigu.mybatis.bean.Employee" id="MyEmpByStep">
<id column="id" property="id"/>
<result column="last_name" property="lastName"/>
<result column="email" property="email"/>
<result column="gender" property="gender"/>
<!-- association定义关联对象的封装规则
select:表明当前属性是调用select指定的方法查出的结果
column:指定将哪一列的值传给这个方法
流程:使用select指定的方法(传入column指定的这列参数的值)查出对象,并封装给property指定的属性
-->
<association property="dept"
select="com.atguigu.mybatis.dao.DepartmentMapper.getDeptById"
column="d_id">
</association>
</resultMap>
<!-- public Employee getEmpByIdStep(Integer id);-->
<select id="getEmpByIdStep" resultMap="MyEmpByStep">
select * from tbl_employee where id=#{id}
<if test="_parameter!=null">
and 1=1
</if>
</select>
<!-- 可以使用延迟加载(懒加载);(按需加载)
Employee==>Dept:
我们每次查询Employee对象的时候,都将一起查询出来。
部门信息在我们使用的时候再去查询;
分段查询的基础之上加上两个配置:
-->
<!-- ==================association============================ -->
<!--
场景二:
查询部门的时候将部门对应的所有员工信息也查询出来:注释在DepartmentMapper.xml中
-->
<!-- public List<Employee> getEmpsByDeptId(Integer deptId); -->
<select id="getEmpsByDeptId" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee where d_id=#{deptId}
</select>
<!-- =======================鉴别器============================ -->
<!-- <discriminator javaType=""></discriminator>
鉴别器:mybatis可以使用discriminator判断某列的值,然后根据某列的值改变封装行为
封装Employee:
如果查出的是女生:就把部门信息查询出来,否则不查询;
如果是男生,把last_name这一列的值赋值给email;
-->
<resultMap type="com.atguigu.mybatis.bean.Employee" id="MyEmpDis">
<id column="id" property="id"/>
<result column="last_name" property="lastName"/>
<result column="email" property="email"/>
<result column="gender" property="gender"/>
<!--
column:指定判定的列名
javaType:列值对应的java类型 -->
<discriminator javaType="string" column="gender">
<!--女生 resultType:指定封装的结果类型;不能缺少。/resultMap-->
<case value="0" resultType="com.atguigu.mybatis.bean.Employee">
<association property="dept"
select="com.atguigu.mybatis.dao.DepartmentMapper.getDeptById"
column="d_id">
</association>
</case>
<!--男生 ;如果是男生,把last_name这一列的值赋值给email; -->
<case value="1" resultType="com.atguigu.mybatis.bean.Employee">
<id column="id" property="id"/>
<result column="last_name" property="lastName"/>
<result column="last_name" property="email"/>
<result column="gender" property="gender"/>
</case>
</discriminator>
</resultMap>
</mapper>
Bean
Employee.java
package com.atguigu.mybatis.bean;
import java.io.Serializable;
import org.apache.ibatis.type.Alias;
@Alias("emp")
public class Employee implements Serializable{
private static final long serialVersionUID = 1L;
private Integer id;
private String lastName;
private String email;
private String gender;
private Department dept;
public Employee() {
super();
}
public Employee(Integer id, String lastName, String email, String gender,
Department dept) {
super();
this.id = id;
this.lastName = lastName;
this.email = email;
this.gender = gender;
this.dept = dept;
}
public Employee(Integer id, String lastName, String email, String gender) {
super();
this.id = id;
this.lastName = lastName;
this.email = email;
this.gender = gender;
}
public Department getDept() {
return dept;
}
public void setDept(Department dept) {
this.dept = dept;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
@Override
public String toString() {
return "Employee [id=" + id + ", lastName=" + lastName + ", email="
+ email + ", gender=" + gender + "]";
}
}
Department.java
package com.atguigu.mybatis.bean;
import java.io.Serializable;
import java.util.List;
public class Department implements Serializable{
private static final long serialVersionUID = 1L;
private Integer id;
private String departmentName;
private List<Employee> emps;
public Department(Integer id) {
super();
this.id = id;
}
public Department() {
super();
// TODO Auto-generated constructor stub
}
public List<Employee> getEmps() {
return emps;
}
public void setEmps(List<Employee> emps) {
this.emps = emps;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getDepartmentName() {
return departmentName;
}
public void setDepartmentName(String departmentName) {
this.departmentName = departmentName;
}
@Override
public String toString() {
return "Department [id=" + id + ", departmentName=" + departmentName
+ "]";
}
}
测试类
MyBatisTest.java
package com.atguigu.mybatis.test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
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 com.atguigu.mybatis.bean.Department;
import com.atguigu.mybatis.bean.Employee;
import com.atguigu.mybatis.dao.DepartmentMapper;
import com.atguigu.mybatis.dao.EmployeeMapper;
import com.atguigu.mybatis.dao.EmployeeMapperAnnotation;
import com.atguigu.mybatis.dao.EmployeeMapperPlus;
/**
* 1、接口式编程
* 原生: Dao ====> DaoImpl
* mybatis: Mapper ====> xxMapper.xml
*
* 2、SqlSession代表和数据库的一次会话;用完必须关闭;
* 3、SqlSession和connection一样她都是非线程安全。每次使用都应该去获取新的对象。
* 4、mapper接口没有实现类,但是mybatis会为这个接口生成一个代理对象。
* (将接口和xml进行绑定)
* EmployeeMapper empMapper = sqlSession.getMapper(EmployeeMapper.class);
* 5、两个重要的配置文件:
* mybatis的全局配置文件:包含数据库连接池信息,事务管理器信息等...系统运行环境信息
* sql映射文件:保存了每一个sql语句的映射信息:
* 将sql抽取出来。
*
*
* @author lfy
*
*/
public class MyBatisTest {
public SqlSessionFactory getSqlSessionFactory() throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
return new SqlSessionFactoryBuilder().build(inputStream);
}
/**
* 1、根据xml配置文件(全局配置文件)创建一个SqlSessionFactory对象 有数据源一些运行环境信息
* 2、sql映射文件;配置了每一个sql,以及sql的封装规则等。
* 3、将sql映射文件注册在全局配置文件中
* 4、写代码:
* 1)、根据全局配置文件得到SqlSessionFactory;
* 2)、使用sqlSession工厂,获取到sqlSession对象使用他来执行增删改查
* 一个sqlSession就是代表和数据库的一次会话,用完关闭
* 3)、使用sql的唯一标志来告诉MyBatis执行哪个sql。sql都是保存在sql映射文件中的。
*
* @throws IOException
*/
@Test
public void test() throws IOException {
// 2、获取sqlSession实例,能直接执行已经映射的sql语句
// sql的唯一标识:statement Unique identifier matching the statement to use.
// 执行sql要用的参数:parameter A parameter object to pass to the statement.
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try {
Employee employee = openSession.selectOne(
"com.atguigu.mybatis.EmployeeMapper.selectEmp", 1);
System.out.println(employee);
} finally {
openSession.close();
}
}
@Test
public void test01() throws IOException {
// 1、获取sqlSessionFactory对象
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
// 2、获取sqlSession对象
SqlSession openSession = sqlSessionFactory.openSession();
try {
// 3、获取接口的实现类对象
//会为接口自动的创建一个代理对象,代理对象去执行增删改查方法
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
Employee employee = mapper.getEmpById(1);
System.out.println(mapper.getClass());
System.out.println(employee);
} finally {
openSession.close();
}
}
@Test
public void test02() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperAnnotation mapper = openSession.getMapper(EmployeeMapperAnnotation.class);
Employee empById = mapper.getEmpById(1);
System.out.println(empById);
}finally{
openSession.close();
}
}
/**
* 测试增删改
* 1、mybatis允许增删改直接定义以下类型返回值
* Integer、Long、Boolean、void
* 2、我们需要手动提交数据
* sqlSessionFactory.openSession();===》手动提交
* sqlSessionFactory.openSession(true);===》自动提交
* @throws IOException
*/
@Test
public void test03() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
//1、获取到的SqlSession不会自动提交数据
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
//测试添加
Employee employee = new Employee(null, "jerry4",null, "1");
mapper.addEmp(employee);
System.out.println(employee.getId());
//测试修改
//Employee employee = new Employee(1, "Tom", "[email protected]", "0");
//boolean updateEmp = mapper.updateEmp(employee);
//System.out.println(updateEmp);
//测试删除
//mapper.deleteEmpById(2);
//2、手动提交数据
openSession.commit();
}finally{
openSession.close();
}
}
@Test
public void test04() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
//1、获取到的SqlSession不会自动提交数据
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
//Employee employee = mapper.getEmpByIdAndLastName(1, "tom");
Map<String, Object> map = new HashMap<>();
map.put("id", 2);
map.put("lastName", "Tom");
map.put("tableName", "tbl_employee");
Employee employee = mapper.getEmpByMap(map);
System.out.println(employee);
/*List<Employee> like = mapper.getEmpsByLastNameLike("%e%");
for (Employee employee : like) {
System.out.println(employee);
}*/
/*Map<String, Object> map = mapper.getEmpByIdReturnMap(1);
System.out.println(map);*/
/*Map<String, Employee> map = mapper.getEmpByLastNameLikeReturnMap("%r%");
System.out.println(map);*/
}finally{
openSession.close();
}
}
@Test
public void test05() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperPlus mapper = openSession.getMapper(EmployeeMapperPlus.class);
/*Employee empById = mapper.getEmpById(1);
System.out.println(empById);*/
/*Employee empAndDept = mapper.getEmpAndDept(1);
System.out.println(empAndDept);
System.out.println(empAndDept.getDept());*/
Employee employee = mapper.getEmpByIdStep(3);
System.out.println(employee);
//System.out.println(employee.getDept());
System.out.println(employee.getDept());
}finally{
openSession.close();
}
}
@Test
public void test06() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
DepartmentMapper mapper = openSession.getMapper(DepartmentMapper.class);
/*Department department = mapper.getDeptByIdPlus(1);
System.out.println(department);
System.out.println(department.getEmps());*/
Department deptByIdStep = mapper.getDeptByIdStep(1);
System.out.println(deptByIdStep.getDepartmentName());
System.out.println(deptByIdStep.getEmps());
}finally{
openSession.close();
}
}
}
原文地址:https://www.cnblogs.com/z00377750/p/12397556.html
时间: 2024-10-29 05:02:37