四、Mybatis Mapper配置文件
mapper.xml映射文件中定义了操作数据库的Sql,每个Sql是一个statement,映射文件是MyBatis的核心。
4.1 parameterType输入映射
parameterType配置输入参数的类型。
4.1.1 表结构
CREATE TABLE `users` (
`id` int(11) PRIMARY KEY AUTO_INCREMENT,
`username` varchar(20),
`password` varchar(50),
`realname` varchar(20)
);
INSERT INTO `users` VALUES (1, 'admin', '123456', '管理员');
INSERT INTO `users` VALUES (2, 'tom', '123', '汤姆');
INSERT INTO `users` VALUES (3, 'jerry', '456', '杰瑞');
INSERT INTO `users` VALUES (4, 'zhangsan', '111', '张三');
INSERT INTO `users` VALUES (5, 'lisi', '222', '李四');
4.1.2 实体类
package com.newcapec.entity;
public class Users {
private Integer id;
private String username;
private String password;
private String realname;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getRealname() {
return realname;
}
public void setRealname(String realname) {
this.realname = realname;
}
@Override
public String toString() {
return "Users{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", realname='" + realname + '\'' +
'}';
}
}
4.1.3 简单类型
Java基本数据类型以及包装类,String字符串类型。
mapper接口:
package com.newcapec.mapper;
import com.newcapec.entity.Users;
import java.util.List;
public interface UsersMapper {
List<Users> selectByRealname(String realname);
}
mapper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.newcapec.mapper.UsersMapper">
<select id="selectByRealname" parameterType="java.lang.String" resultType="com.newcapec.entity.Users">
select id,username,password,realname from users where realname like concat('%',#{realname},'%')
</select>
</mapper>
测试:
package com.newcapec;
import com.newcapec.entity.Users;
import com.newcapec.mapper.UsersMapper;
import com.newcapec.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class ParameterTypeTest {
@Test
public void testSimpleParam() {
SqlSession sqlSession = MybatisUtil.getSession();
UsersMapper usersMapper = sqlSession.getMapper(UsersMapper.class);
List<Users> list = usersMapper.selectByRealname("张");
for (Users users : list) {
System.out.println(users);
}
sqlSession.close();
}
}
4.1.4 实体类或自定义类型
开发中通过实体类或pojo类型传递查询条件,查询条件是综合的查询条件,不仅包括实体类中查询条件还包括其它的查询条件,这时可以使用包装对象传递输入参数。
- 自定义类型
分页类:
package com.newcapec.entity;
/**
* 分页类
*/
public class Page {
//当前页码
private Integer pageNum = 1;
//每页条数
private Integer pageSize = 3;
//总页数: 总记录数/每页条数,除不尽+1
private Integer pages;
//总记录数
private Integer total;
/**
* mysql
* 起始偏移量:(当前页码-1)*每页条数
*/
private Integer offset;
/**
* oracle
* 起始条数:(当前页码-1)*每页条数+1
* 结束条数: 当前页码*每页条数
*/
private Integer start;
private Integer end;
public Integer getPageNum() {
return pageNum;
}
public void setPageNum(Integer pageNum) {
this.pageNum = pageNum;
}
public Integer getPageSize() {
return pageSize;
}
public void setPageSize(Integer pageSize) {
this.pageSize = pageSize;
}
public Integer getPages() {
return getTotal() % getPageSize() == 0 ? getTotal() / getPageSize() : getTotal() / getPageSize() + 1;
}
public void setPages(Integer pages) {
this.pages = pages;
}
public Integer getTotal() {
return total;
}
public void setTotal(Integer total) {
this.total = total;
}
public Integer getOffset() {
return (getPageNum() - 1) * getPageSize();
}
public void setOffset(Integer offset) {
this.offset = offset;
}
public Integer getStart() {
return (getPageNum() - 1) * getPageSize() + 1;
}
public void setStart(Integer start) {
this.start = start;
}
public Integer getEnd() {
return getPageNum() * getPageSize();
}
public void setEnd(Integer end) {
this.end = end;
}
}
复合类:UsersQuery
package com.newcapec.entity;
/**
* 多条件查询复合类
*/
public class UsersQuery {
private Users users;
private Page page;
public Users getUsers() {
return users;
}
public void setUsers(Users users) {
this.users = users;
}
public Page getPage() {
return page;
}
public void setPage(Page page) {
this.page = page;
}
}
- mapper接口
List<Users> selectByPage(Page page);
List<Users> selectByRealnameAndPage(UsersQuery usersQuery);
- mapper文件
<select id="selectByPage" parameterType="com.newcapec.entity.Page" resultType="com.newcapec.entity.Users">
select id,username,password,realname from users order by id limit #{offset}, #{pageSize}
</select>
<select id="selectByRealnameAndPage" parameterType="com.newcapec.entity.UsersQuery" resultType="com.newcapec.entity.Users">
select id,username,password,realname from users
where realname like concat('%',#{users.realname},'%')
order by id limit #{page.offset}, #{page.pageSize}
</select>
- 测试
@Test
public void testClassParam1() {
SqlSession sqlSession = MybatisUtil.getSession();
UsersMapper usersMapper = sqlSession.getMapper(UsersMapper.class);
Page page = new Page();
page.setPageNum(1);
System.out.println("mysql起始偏移量:" + page.getOffset());
System.out.println("起始条数:" + page.getStart());
System.out.println("结束条数:" + page.getEnd());
List<Users> list = usersMapper.selectByPage(page);
for (Users users : list) {
System.out.println(users);
}
sqlSession.close();
}
@Test
public void testPojoParam2() {
SqlSession sqlSession = MybatisUtil.getSession();
UsersMapper usersMapper = sqlSession.getMapper(UsersMapper.class);
Page page = new Page();
page.setPageNum(1);
Users users = new Users();
users.setRealname("张");
UsersQuery usersQuery = new UsersQuery();
usersQuery.setPage(page);
usersQuery.setUsers(users);
List<Users> list = usersMapper.selectByRealnameAndPage(usersQuery);
for (Users u : list) {
System.out.println(u);
}
sqlSession.close();
}
4.1.5 Map类型
mapper接口:
List<Users> selectUseMap(Map<String, Object> map);
mapper文件:
<select id="selectUseMap" parameterType="java.util.HashMap" resultType="com.newcapec.entity.Users">
select id,username,password,realname from users
where realname like concat('%',#{name},'%')
order by id limit #{begin}, #{size}
</select>
测试:
@Test
public void testMapParam() {
SqlSession sqlSession = MybatisUtil.getSession();
UsersMapper usersMapper = sqlSession.getMapper(UsersMapper.class);
Map<String, Object> map = new HashMap<>();
map.put("name", "李");
map.put("size", 5);
map.put("begin", 0);
List<Users> list = usersMapper.selectUseMap(map);
for (Users u : list) {
System.out.println(u);
}
sqlSession.close();
}
4.1.6 多输入参数
MyBatis中允许有多个输入参数,可使用@Param注解。
这种做法类似与Map类型的输入参数,其中@Param注解的value属性值为Map的key,在映射文件中通过ognl可获取对应的value,并且parameterType可以不指定类型。
mapper接口:
Users login(@Param("uname") String username, @Param("pwd") String password);
mapper文件:
<select id="login" parameterType="java.util.HashMap" resultType="com.newcapec.entity.Users">
select id,username,password,realname from users
where username=#{uname} and password=#{pwd}
</select>
测试:
@Test
public void testMultiParam() {
SqlSession sqlSession = MybatisUtil.getSession();
UsersMapper usersMapper = sqlSession.getMapper(UsersMapper.class);
Users users = usersMapper.login("jerry", "456");
System.out.println(users);
sqlSession.close();
}
4.2 resultType输出映射
4.2.1 表结构
CREATE TABLE `person` (
`id` int(11) PRIMARY KEY AUTO_INCREMENT,
`person_name` varchar(20),
`person_age` int(4),
`person_address` varchar(50)
);
INSERT INTO `person` VALUES (1, '曹操', 40, '洛阳');
INSERT INTO `person` VALUES (2, '刘备', 38, '成都');
INSERT INTO `person` VALUES (3, '孙权', 29, '杭州');
INSERT INTO `person` VALUES (4, '关羽', 35, '荆州');
INSERT INTO `person` VALUES (5, '张飞', 32, '成都');
INSERT INTO `person` VALUES (6, '曹仁', 28, '许都');
4.2.2 实体类
package com.newcapec.entity;
public class Person {
private Integer id;
private String personName;
private Integer personAge;
private String personAddress;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getPersonName() {
return personName;
}
public void setPersonName(String personName) {
this.personName = personName;
}
public Integer getPersonAge() {
return personAge;
}
public void setPersonAge(Integer personAge) {
this.personAge = personAge;
}
public String getPersonAddress() {
return personAddress;
}
public void setPersonAddress(String personAddress) {
this.personAddress = personAddress;
}
@Override
public String toString() {
return "Person{" +
"id=" + id +
", personName='" + personName + '\'' +
", personAge=" + personAge +
", personAddress='" + personAddress + '\'' +
'}';
}
}
4.2.3 简单类型
查询出来的结果集只有一行且一列,可以使用简单类型进行输出映射。
mapper接口:
package com.newcapec.mapper;
public interface PersonMapper {
// 查询Person的总数量
Integer selectCount();
}
mapper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.newcapec.mapper.PersonMapper">
<select id="selectCount" resultType="java.lang.Integer">
select count(1) from person
</select>
</mapper>
测试:
public class ResultTypeTest {
@Test
public void testSimpleResult() {
SqlSession sqlSession = MybatisUtil.getSession();
PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
int total = personMapper.selectCount();
System.out.println("总记录数:" + total);
sqlSession.close();
}
}
4.2.4 实体类对象和列表
不管是输出的实体类是单个对象还是一个列表(list中包括实体类对象),在mapper.xml中resultType指定的类型是一样的
在原始Dao的方式中,通过selectOne和selectList方法来区分返回值为单个对象或集合列表,而在mapper代理中,则通过接口中定义的方法返回值来区分。
mapper接口:
Person selectById(Integer id);
List<Person> selectAll();
mapper文件:
<select id="selectById" parameterType="java.lang.Integer" resultType="com.newcapec.entity.Person">
select id,person_name personName,person_age personAge,person_address personAddress from person where id=#{id}
</select>
<select id="selectAll" resultType="com.newcapec.entity.Person">
select id,person_name personName,person_age personAge,person_address personAddress from person
</select>
测试:
@Test
public void testResultType1() {
SqlSession sqlSession = MybatisUtil.getSession();
PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
Person person = personMapper.selectById(1);
System.out.println(person);
sqlSession.close();
}
@Test
public void testResultType2() {
SqlSession sqlSession = MybatisUtil.getSession();
PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
List<Person> list = personMapper.selectAll();
for (Person person : list) {
System.out.println(person);
}
sqlSession.close();
}
4.2.5 resultMap
-
resultType可以指定将查询结果映射为实体类,但需要实体类的属性名和SQL查询的列名一致方可映射成功,当然如果开启下划线转驼峰 或 Sql设置列别名,也可以自动映射。
-
如果SQL查询字段名和实体类的属性名不一致,可以通过resultMap将字段名和属性名作一个对应关系,resultMap实质上还会将查询结果映射到实体类对象中。
-
resultMap可以实现将查询结果映射为复合型的实体类,比如在查询结果映射对象中包括实体类和list实现一对一查询和一对多查询。
mapper接口:
List<Person> select();
mapper文件:
使用resultMap作为statement的输出映射类型。
<resultMap id="selectResultMap" type="com.newcapec.entity.Person">
<id property="id" column="id"/>
<result property="personName" column="person_name"/>
<result property="personAge" column="person_age"/>
<result property="personAddress" column="person_address"/>
</resultMap>
<select id="select" resultMap="selectResultMap">
select id,person_name,person_age,person_address from person
</select>
-
resultType: 自动映射
-
resultMap: 手动映射
-
id: 唯一标识,名称;
-
type: 手动映射的java类型
-
子标签
<id/>
配置数据库表中的主键和实体类中属性的对应关系 -
子标签
<result/>
配置数据库表中的普通字段和实体类中属性的对应关系-
property:实体类中的成员变量名
-
column:结果集中的字段名称
-
javaType:实体类成员变量的类型,由mybaits自动识别,可不配置
-
jdbcType:表字段的类型,由mybaits自动识别,可不配置
-
typeHandler:自定义类型处理器,用的相对比较少
-
-
测试:
@Test
public void testResultMap() {
SqlSession sqlSession = MybatisUtil.getSession();
PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
List<Person> list = personMapper.select();
for (Person person : list) {
System.out.println(person);
}
sqlSession.close();
}
4.3 动态SQL
4.3.1 什么是动态SQL
动态Sql是指MyBatis核心对Sql语句进行灵活操作,通过表达式进行判断,对Sql进行灵活拼接、组装。
比如:
我们要查询姓名中带 M 和 高于 1000的员工信息;
可能有时候我们需要不带条件查询;
可能有时候我们需要模糊查询;
可能有时候需要根据多条件查询;
动态SQL可以帮助我们解决这些问题;
通过mybatis提供的各种标签方法实现动态拼接sql。
4.3.2 if标签
判断标签,当参数符合判断条件拼接SQL语句。
实体类:
package com.newcapec.entity;
import java.util.Date;
public class Emp {
private Integer empno;
private String ename;
private String job;
private Integer mgr;
private Date hiredate;
private Double sal;
private Double comm;
private Integer deptno;
private String gender;
public Integer getEmpno() {
return empno;
}
public void setEmpno(Integer empno) {
this.empno = empno;
}
public String getEname() {
return ename;
}
public void setEname(String ename) {
this.ename = ename;
}
public String getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
public Integer getMgr() {
return mgr;
}
public void setMgr(Integer mgr) {
this.mgr = mgr;
}
public Date getHiredate() {
return hiredate;
}
public void setHiredate(Date hiredate) {
this.hiredate = hiredate;
}
public Double getSal() {
return sal;
}
public void setSal(Double sal) {
this.sal = sal;
}
public Double getComm() {
return comm;
}
public void setComm(Double comm) {
this.comm = comm;
}
public Integer getDeptno() {
return deptno;
}
public void setDeptno(Integer deptno) {
this.deptno = deptno;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
@Override
public String toString() {
return "Emp{" +
"empno=" + empno +
", ename='" + ename + '\'' +
", job='" + job + '\'' +
", mgr=" + mgr +
", hiredate=" + hiredate +
", sal=" + sal +
", comm=" + comm +
", deptno=" + deptno +
", gender='" + gender + '\'' +
'}';
}
}
mapper接口:
public interface EmpMapper {
List<Emp> selectUseIf(Emp emp);
}
mapper文件:
<select id="selectUseIf" parameterType="com.newcapec.entity.Emp" resultType="com.newcapec.entity.Emp">
select empno,ename,job,mgr,hiredate,sal,comm,deptno from emp
where
<!--
注意:判断条件中使用的变量为实体类或输入参数的属性
空字符串的判断仅能使用在字符串类型的属性中
-->
<if test="ename != null and ename != ''">
ename like concat('%',#{ename},'%')
</if>
<if test="sal != null">
and sal=#{sal}
</if>
<if test="deptno != null">
and deptno=#{deptno}
</if>
</select>
测试:
/*
* 动态sql测试
*/
public class DynamicSqlTest {
@Test
public void testIf() {
SqlSession sqlSession = MybatisUtil.getSession();
EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
Emp emp = new Emp();
emp.setEname("S");
emp.setSal(1300.0);
emp.setDeptno(20);
List<Emp> list = empMapper.selectUseIf(emp);
for (Emp e : list) {
System.out.println(e);
}
sqlSession.close();
}
}
4.3.3 where标签
where标签,替代where关键字。
1、当where标签内所有的条件都不成立,不会拼接where关键字,只要有一个条件成立就会在SQL语句中拼接where关键字。
2、where标签会自动剔除条件头部的and或者or关键字。
mapper接口:
List<Emp> selectUseWhere(Emp emp);
mapper文件:
<select id="selectUseWhere" parameterType="com.newcapec.entity.Emp" resultType="com.newcapec.entity.Emp">
select empno,ename,job,mgr,hiredate,sal,comm,deptno from emp
<where>
<if test="ename != null and ename != ''">
ename like concat('%',#{ename},'%')
</if>
<if test="sal != null">
and sal=#{sal}
</if>
<if test="deptno != null">
and deptno=#{deptno}
</if>
</where>
</select>
测试:
@Test
public void testWhere() {
SqlSession sqlSession = MybatisUtil.getSession();
EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
Emp emp = new Emp();
emp.setEname("S");
emp.setSal(1300.0);
emp.setDeptno(20);
List<Emp> list = empMapper.selectUseWhere(emp);
for (Emp e : list) {
System.out.println(e);
}
sqlSession.close();
}
4.3.4 set标签
set标签,替代set关键字。
1、当set标签内所有的条件都不成立,不会拼接set关键字,只要有一个条件成立就会在SQL语句中拼接set关键字。
2、注意:如果set包含的内容为空SQL语句会出错。
3、set标签会自动剔除条件末尾的任何不相关的逗号。
mapper接口:
void updateUseSet(Emp emp);
mapper文件:
<update id="updateUseSet" parameterType="com.newcapec.entity.Emp">
update emp
<set>
<if test="ename != null">
ename=#{ename},
</if>
<if test="job != null">
job=#{job},
</if>
<if test="mgr != null">
mgr=#{mgr},
</if>
<if test="hiredate != null">
hiredate=#{hiredate},
</if>
<if test="sal != null">
sal=#{sal},
</if>
<if test="comm != null">
comm=#{comm},
</if>
<if test="deptno != null">
deptno=#{deptno},
</if>
</set>
where empno=#{empno}
</update>
测试:
@Test
public void testSet() {
SqlSession sqlSession = MybatisUtil.getSession();
EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
Emp emp = new Emp();
emp.setEmpno(7938);
emp.setEname("JACK");
emp.setJob("MANAGER");
emp.setMgr(7844);
emp.setSal(5600.0);
emp.setComm(1200.0);
emp.setHiredate(new Date());
emp.setDeptno(30);
empMapper.updateUseSet(emp);
sqlSession.commit();
sqlSession.close();
}
4.3.5 trim标签
trim标签属性解析:
-
prefix:前缀,包含内容前加上某些字符。
-
suffix:后缀,包含内容后加上某些字符。
-
prefixOverrides:剔除包含内容前的某些字符。
-
suffixOverrides:剔除包含内容后的某些字符。
mapper接口:
void insertUseTrim(Emp emp);
mapper文件:
<insert id="insertUseTrim" parameterType="com.newcapec.entity.Emp">
insert into emp
<trim prefix="(" suffix=")" suffixOverrides=",">
<if test="ename != null">
ename,
</if>
<if test="job != null">
job,
</if>
<if test="mgr != null">
mgr,
</if>
<if test="hiredate != null">
hiredate,
</if>
<if test="sal != null">
sal,
</if>
<if test="comm != null">
comm,
</if>
<if test="deptno != null">
deptno,
</if>
</trim>
<trim prefix=" values(" suffix=")" suffixOverrides=",">
<if test="ename != null">
#{ename},
</if>
<if test="job != null">
#{job},
</if>
<if test="mgr != null">
#{mgr},
</if>
<if test="hiredate != null">
#{hiredate},
</if>
<if test="sal != null">
#{sal},
</if>
<if test="comm != null">
#{comm},
</if>
<if test="deptno != null">
#{deptno},
</if>
</trim>
</insert>
测试:
@Test
public void testTrim() {
SqlSession sqlSession = MybatisUtil.getSession();
EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
Emp emp = new Emp();
emp.setEname("CHRIS");
emp.setJob("CLERK");
emp.setMgr(1);
emp.setSal(3400.0);
emp.setComm(800.0);
emp.setHiredate(new Date());
emp.setDeptno(10);
empMapper.insertUseTrim(emp);
sqlSession.commit();
sqlSession.close();
}
代替where标签:
<select id="selectUseTrim" parameterType="com.newcapec.entity.Emp" resultType="com.newcapec.entity.Emp">
select empno,ename,job,mgr,hiredate,sal,comm,deptno from emp
<trim prefix="where" prefixOverrides="and|or">
<if test="ename != null and ename != ''">
ename like concat('%',#{ename},'%')
</if>
<if test="sal != null">
and sal=#{sal}
</if>
<if test="deptno != null">
and deptno=#{deptno}
</if>
</trim>
</select>
代替set标签:
<update id="updateUseTrim" parameterType="com.newcapec.entity.Emp">
update emp
<trim prefix="set" suffixOverrides=",">
<if test="ename != null">
ename=#{ename},
</if>
<if test="job != null">
job=#{job},
</if>
<if test="mgr != null">
mgr=#{mgr},
</if>
<if test="hiredate != null">
hiredate=#{hiredate},
</if>
<if test="sal != null">
sal=#{sal},
</if>
<if test="comm != null">
comm=#{comm},
</if>
<if test="deptno != null">
deptno=#{deptno},
</if>
</trim>
where empno=#{empno}
</update>
4.3.6 foreach标签
向SQL传递数组或list,MyBatis使用foreach解析。
属性解析:
-
collection: 遍历的数组或集合对象名称。
-
SQL只接收一个数组参数,这时SQL解析参数的名称MyBatis固定为array。
-
SQL只接收一个List参数,这时SQL解析参数的名称MyBatis固定为list。
-
如果是通过一个实体类或自定义类型的属性传递到SQL的数组或List集合,则参数的名称为实体类或自定义类型中的属性名。
-
-
index: 为数组的下标。
-
item: 每个遍历生成对象中。
-
open: 开始遍历时拼接的串。
-
close: 结束遍历时拼接的串。
-
separator: 遍历的两个对象中需要拼接的串。
mapper接口:
void deleteUseForeach(Integer[] ids);
void insertUseForeach(List<Emp> empList);
mapper文件:
<delete id="deleteUseForeach" parameterType="java.lang.Integer">
<!--delete from emp where empno in (1,2,3,4)-->
delete from emp where empno in
<foreach collection="array" open="(" close=")" separator="," item="id">
#{id}
</foreach>
</delete>
<insert id="insertUseForeach" parameterType="com.newcapec.entity.Emp">
insert into emp(ename,job,mgr,hiredate,sal,comm,deptno) values
<foreach collection="list" separator="," item="emp">
(#{emp.ename},#{emp.job},#{emp.mgr},#{emp.hiredate},#{emp.sal},#{emp.comm},#{emp.deptno})
</foreach>
</insert>
测试:
@Test
public void testForeach() {
SqlSession sqlSession = MybatisUtil.getSession();
EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
empMapper.deleteUseForeach(new Integer[]{1, 2, 3, 4});
sqlSession.commit();
sqlSession.close();
}
@Test
public void testForeach2() {
SqlSession sqlSession = MybatisUtil.getSession();
EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
List<Emp> empList = new ArrayList<>();
for (int i = 1; i <= 3; i++) {
Emp emp = new Emp();
emp.setEname("TOM" + i);
emp.setJob("CLERK" + i);
emp.setMgr(1);
emp.setSal(4567.0);
emp.setComm(123.0);
emp.setHiredate(new Date());
emp.setDeptno(10);
empList.add(emp);
}
empMapper.insertUseForeach(empList);
//sqlSession.commit();
sqlSession.close();
}
4.3.7 choose标签
choose标签、when标签、otherwise标签的组合,类似于if-else-if判断。
<select id="">
select...
<choose>
<when test="">
</when>
<when test="">
</when>
<otherwise>
</otherwise>
</choose>
</select>
4.3.8 SQL片段
将实现的动态SQL判断代码块抽取出来,组成一个SQL片段,其它的statement中就可以引用SQL片段,方便程序员进行开发。
注意:在SQL片段中不要包括where标签。
<sql id="feildSql">
empno,ename,job,mgr,hiredate,sal,comm,deptno
</sql>
<sql id="whereSql">
<if test="ename != null and ename != ''">
ename like concat('%',#{ename},'%')
</if>
<if test="sal != null">
and sal=#{sal}
</if>
<if test="deptno != null">
and deptno=#{deptno}
</if>
</sql>
<select id="selectUseSql" parameterType="com.newcapec.entity.Emp" resultType="com.newcapec.entity.Emp">
select
<include refid="feildSql"></include>
from emp
<where>
<include refid="whereSql"></include>
</where>
</select>