mybatis视频教程2-动态参数

package com.atguigu.mybatis.dao;import java.util.List;import org.apache.ibatis.annotations.Param;import com.atguigu.mybatis.bean.Employee;public interface EmployeeMapperDynamicSQL { public List<Employee> getEmpsTestInnerParameter(Employee employee); //携带了哪个字段查询条件就带上这个字段的值
public List<Employee> getEmpsByConditionIf(Employee employee); public List<Employee> getEmpsByConditionTrim(Employee employee); public List<Employee> getEmpsByConditionChoose(Employee employee); public void updateEmp(Employee employee); //查询员工id'在给定集合中的
public List<Employee> getEmpsByConditionForeach(@Param("ids")List<Integer> ids); public void addEmps(@Param("emps")List<Employee> emps);}

<?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.EmployeeMapperDynamicSQL">
<!--
• if:判断
• choose (when, otherwise):分支选择；带了break的swtich-case
如果带了id就用id查，如果带了lastName就用lastName查;只会进入其中一个
• trim 字符串截取(where(封装查询条件), set(封装修改条件))
• foreach 遍历集合
-->
<!-- 查询员工，要求，携带了哪个字段查询条件就带上这个字段的值 -->
<!-- public List<Employee> getEmpsByConditionIf(Employee employee); -->
<select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<!-- where -->
<where>
<!-- test：判断表达式（OGNL）
OGNL参照PPT或者官方文档。
c:if test
从参数中取值进行判断 遇见特殊符号应该去写转义字符：
&&：
-->
<if test="id!=null">
id=#{id}
</if>
<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
and last_name like #{lastName}
</if>
<if test="email!=null and email.trim()!=&quot;&quot;">
and email=#{email}
</if>
<!-- ognl会进行字符串与数字的转换判断 "0"==0 -->
<if test="gender==0 or gender==1">
and gender=#{gender}
</if>
</where>
</select> <!--public List<Employee> getEmpsByConditionTrim(Employee employee); -->
<select id="getEmpsByConditionTrim" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<!-- 后面多出的and或者or where标签不能解决
prefix="":前缀：trim标签体中是整个字符串拼串 后的结果。
prefix给拼串后的整个字符串加一个前缀
prefixOverrides="":
前缀覆盖： 去掉整个字符串前面多余的字符
suffix="":后缀
suffix给拼串后的整个字符串加一个后缀
suffixOverrides=""
后缀覆盖：去掉整个字符串后面多余的字符 -->
<!-- 自定义字符串的截取规则 -->
<trim prefix="where" suffixOverrides="and">
<if test="id!=null">
id=#{id} and
</if>
<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
last_name like #{lastName} and
</if>
<if test="email!=null and email.trim()!=&quot;&quot;">
email=#{email} and
</if>
<!-- ognl会进行字符串与数字的转换判断 "0"==0 -->
<if test="gender==0 or gender==1">
gender=#{gender}
</if>
</trim>
</select> <!-- public List<Employee> getEmpsByConditionChoose(Employee employee); -->
<select id="getEmpsByConditionChoose" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<where>
<!-- 如果带了id就用id查，如果带了lastName就用lastName查;只会进入其中一个 -->
<choose>
<when test="id!=null">
id=#{id}
</when>
<when test="lastName!=null">
last_name like #{lastName}
</when>
<when test="email!=null">
email = #{email}
</when>
<otherwise>
gender = 0
</otherwise>
</choose>
</where>
</select> <!--public void updateEmp(Employee employee); -->
<update id="updateEmp">
<!-- Set标签的使用 -->
update tbl_employee
<set>
<if test="lastName!=null">
last_name=#{lastName},
</if>
<if test="email!=null">
email=#{email},
</if>
<if test="gender!=null">
gender=#{gender}
</if>
</set>
where id=#{id}
<!--
Trim：更新拼串
update tbl_employee
<trim prefix="set" suffixOverrides=",">
<if test="lastName!=null">
last_name=#{lastName},
</if>
<if test="email!=null">
email=#{email},
</if>
<if test="gender!=null">
gender=#{gender}
</if>
</trim>
where id=#{id} -->
</update> <!--public List<Employee> getEmpsByConditionForeach(List<Integer> ids); -->
<select id="getEmpsByConditionForeach" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<!--
collection：指定要遍历的集合：
list类型的参数会特殊处理封装在map中，map的key就叫list
item：将当前遍历出的元素赋值给指定的变量
separator:每个元素之间的分隔符
open：遍历出所有结果拼接一个开始的字符
close:遍历出所有结果拼接一个结束的字符
index:索引。遍历list的时候是index就是索引，item就是当前值
遍历map的时候index表示的就是map的key，item就是map的值 #{变量名}就能取出变量的值也就是当前遍历出的元素
-->
<foreach collection="ids" item="item_id" separator=","
open="where id in(" close=")">
#{item_id}
</foreach>
</select> <!-- 批量保存 -->
<!--public void addEmps(@Param("emps")List<Employee> emps); -->
<!--MySQL下批量保存：可以foreach遍历 mysql支持values(),(),()语法-->
<insert id="addEmps">
insert into tbl_employee(
<include refid="insertColumn"></include>
)
values
<foreach collection="emps" item="emp" separator=",">
(#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})
</foreach>
</insert><!-- --> <!-- 这种方式需要数据库连接属性allowMultiQueries=true；
这种分号分隔多个sql可以用于其他的批量操作（删除，修改） -->
<!-- <insert id="addEmps">
<foreach collection="emps" item="emp" separator=";">
insert into tbl_employee(last_name,email,gender,d_id)
values(#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})
</foreach>
</insert> --> <!-- Oracle数据库批量保存：
Oracle不支持values(),(),()
Oracle支持的批量方式
1、多个insert放在begin - end里面
begin
insert into employees(employee_id,last_name,email)
values(employees_seq.nextval,'test_001','test_001@atguigu.com');
insert into employees(employee_id,last_name,email)
values(employees_seq.nextval,'test_002','test_002@atguigu.com');
end;
2、利用中间表：
insert into employees(employee_id,last_name,email)
select employees_seq.nextval,lastName,email from(
select 'test_a_01' lastName,'test_a_e01' email from dual
union
select 'test_a_02' lastName,'test_a_e02' email from dual
union
select 'test_a_03' lastName,'test_a_e03' email from dual
)
-->
<insert id="addEmps" databaseId="oracle">
<!-- oracle第一种批量方式 -->
<!-- <foreach collection="emps" item="emp" open="begin" close="end;">
insert into employees(employee_id,last_name,email)
values(employees_seq.nextval,#{emp.lastName},#{emp.email});
</foreach> --> <!-- oracle第二种批量方式 -->
insert into employees(
<!-- 引用外部定义的sql -->
<include refid="insertColumn">
<property name="testColomn" value="abc"/>
</include>
)
<foreach collection="emps" item="emp" separator="union"
open="select employees_seq.nextval,lastName,email from("
close=")">
select #{emp.lastName} lastName,#{emp.email} email from dual
</foreach>
</insert> <!-- 两个内置参数：
不只是方法传递过来的参数可以被用来判断，取值。。。
mybatis默认还有两个内置参数：
_parameter:代表整个参数
单个参数：_parameter就是这个参数
多个参数：参数会被封装为一个map；_parameter就是代表这个map _databaseId:如果配置了databaseIdProvider标签。
_databaseId就是代表当前数据库的别名oracle
--> <!--public List<Employee> getEmpsTestInnerParameter(Employee employee); -->
<select id="getEmpsTestInnerParameter" resultType="com.atguigu.mybatis.bean.Employee">
<!-- bind：可以将OGNL表达式的值绑定到一个变量中，方便后来引用这个变量的值 -->
<bind name="_lastName" value="'%'+lastName+'%'"/>
<if test="_databaseId=='mysql'">
select * from tbl_employee
<if test="_parameter!=null">
where last_name like #{lastName}
</if>
</if>
<if test="_databaseId=='oracle'">
select * from employees
<if test="_parameter!=null">
where last_name like #{_parameter.lastName}
</if>
</if>
</select> <!--
抽取可重用的sql片段。方便后面引用
1、sql抽取：经常将要查询的列名，或者插入用的列名抽取出来方便引用
2、include来引用已经抽取的sql：
3、include还可以自定义一些property，sql标签内部就能使用自定义的属性
include-property：取值的正确方式${prop},
#{不能使用这种方式}
-->
<sql id="insertColumn">
<if test="_databaseId=='oracle'">
employee_id,last_name,email
</if>
<if test="_databaseId=='mysql'">
last_name,email,gender,d_id
</if>
</sql></mapper>

<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
and last_name like #{lastName}
</if>

package com.atguigu.mybatis.test;import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
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.EmployeeMapperDynamicSQL;
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);
} @Test
public void testInnerParam() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
Employee employee2 = new Employee();
employee2.setId(1);
employee2.setLastName("%e%");
List<Employee> list = mapper.getEmpsByConditionIf(employee2);
for (Employee employee : list) {
System.out.println(employee);
}
}finally{
openSession.close();
}
} @Test
public void testBatchSave() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
List<Employee> emps = new ArrayList<>();
emps.add(new Employee(null, "smith0x1", "smith0x1@atguigu.com", "1",new Department(1)));
emps.add(new Employee(null, "allen0x1", "allen0x1@atguigu.com", "0",new Department(1)));
mapper.addEmps(emps);
openSession.commit();
}finally{
openSession.close();
}
} @Test
public void testDynamicSql() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
//select * from tbl_employee where id=? and last_name like ?
//测试if\where
Employee employee = new Employee(1, "Admin", null, null);
/* List<Employee> emps = mapper.getEmpsByConditionIf(employee );
for (Employee emp : emps) {
System.out.println(emp);
}*/ //查询的时候如果某些条件没带可能sql拼装会有问题
//1、给where后面加上1=1，以后的条件都and xxx.
//2、mybatis使用where标签来将所有的查询条件包括在内。mybatis就会将where标签中拼装的sql，多出来的and或者or去掉
//where只会去掉第一个多出来的and或者or。 //测试Trim
/*List<Employee> emps2 = mapper.getEmpsByConditionTrim(employee);
for (Employee emp : emps2) {
System.out.println(emp);
}*/ //测试choose
/*List<Employee> list = mapper.getEmpsByConditionChoose(employee);
for (Employee emp : list) {
System.out.println(emp);
}*/ //测试set标签
/*mapper.updateEmp(employee);
openSession.commit();*/ List<Employee> list = mapper.getEmpsByConditionForeach(Arrays.asList(1,2));
for (Employee emp : list) {
System.out.println(emp);
} }finally{
openSession.close();
}
} /**
* 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", "jerry@atguigu.com", "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();
}
} }
我们来看下运行的效果

DEBUG 04-26 06:52:48,375 ==> Preparing: select * from tbl_employee WHERE id=? and last_name like ? (BaseJdbcLogger.java:145)
DEBUG 04-26 06:52:48,430 ==> Parameters: 1(Integer), %e%(String) (BaseJdbcLogger.java:145)
DEBUG 04-26 06:52:48,452 <== Total: 0 (BaseJdbcLogger.java:145)

注意点：

上面中如果将where标签去掉，写成下面的形式会存在问题

在查询的时候，如果id字段为null会出现sql字符串拼接错误

DEBUG 04-26 07:02:46,554 ==> Preparing: select * from tbl_employee and last_name like ? (BaseJdbcLogger.java:145)
DEBUG 04-26 07:02:46,612 ==> Parameters: %e%(String) (BaseJdbcLogger.java:145)

解决办法除了上面添加where字段之外，还可以使用下面的语句增加where 1 =1

但是上面的代码还存在问题

DEBUG 04-26 07:08:12,950 ==> Preparing: select * from tbl_employee where 1=1 id=? and last_name like ? (BaseJdbcLogger.java:145)
DEBUG 04-26 07:08:13,018 ==> Parameters: 1(Integer), %e%(String) (BaseJdbcLogger.java:145)

我们应该后续的所有判断条件上都增加and标签

<select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<where>
<!-- where -->
<!-- test：判断表达式（OGNL）
OGNL参照PPT或者官方文档。
c:if test
从参数中取值进行判断 遇见特殊符号应该去写转义字符：
&&：
-->
<if test="id!=null">
and id=#{id}
</if>
<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
and last_name like #{lastName}
</if>
<if test="email!=null and email.trim()!=&quot;&quot;">
and email=#{email}
</if>
<!-- ognl会进行字符串与数字的转换判断 "0"==0 -->
<if test="gender==0 or gender==1">
and gender=#{gender}
</if>
</where>
</select>

@Test
public void testInnerParam() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
Employee employee2 = new Employee();
employee2.setId(null);
employee2.setLastName("%e%");
employee2.setEmail(null);
employee2.setGender("0");
List<Employee> list = mapper.getEmpsByConditionIf(employee2);
for (Employee employee : list) {
System.out.println(employee);
}
}finally{
openSession.close();
}
}

DEBUG 04-26 07:14:15,499 ==> Preparing: select * from tbl_employee WHERE last_name like ? and gender=? (BaseJdbcLogger.java:145)
DEBUG 04-26 07:14:15,556 ==> Parameters: %e%(String), 0(String) (BaseJdbcLogger.java:145)
DEBUG 04-26 07:14:15,577 <== Total: 0 (BaseJdbcLogger.java:145)

<select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<where>
<!-- where -->
<!-- test：判断表达式（OGNL）
OGNL参照PPT或者官方文档。
c:if test
从参数中取值进行判断 遇见特殊符号应该去写转义字符：
&&：
-->
<if test="id!=null">
id=#{id} and
</if>
<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
last_name like #{lastName} and
</if>
<if test="email!=null and email.trim()!=&quot;&quot;">
email=#{email} and
</if>
<!-- ognl会进行字符串与数字的转换判断 "0"==0 -->
<if test="gender==0 or gender==1">
gender=#{gender}
</if>
</where>
</select>

@Test
public void testInnerParam() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
Employee employee2 = new Employee();
employee2.setId(1);
employee2.setLastName("%e%");
employee2.setEmail(null);
List<Employee> list = mapper.getEmpsByConditionIf(employee2);
for (Employee employee : list) {
System.out.println(employee);
}
}finally{
openSession.close();
}
}

<select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<trim suffixOverrides="and">
<where>
<!-- where -->
<!-- test：判断表达式（OGNL）
OGNL参照PPT或者官方文档。
c:if test
从参数中取值进行判断 遇见特殊符号应该去写转义字符：
&&：
-->
<if test="id!=null">
id=#{id} and
</if>
<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
last_name like #{lastName} and
</if>
<if test="email!=null and email.trim()!=&quot;&quot;">
email=#{email} and
</if>
<!-- ognl会进行字符串与数字的转换判断 "0"==0 -->
<if test="gender==0 or gender==1">
gender=#{gender}
</if>
</where>
</trim>
</select>

<select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<trim prefix="where" suffixOverrides="and">
<!-- where -->
<!-- test：判断表达式（OGNL）
OGNL参照PPT或者官方文档。
c:if test
从参数中取值进行判断 遇见特殊符号应该去写转义字符：
&&：
-->
<if test="id!=null">
id=#{id} and
</if>
<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
last_name like #{lastName} and
</if>
<if test="email!=null and email.trim()!=&quot;&quot;">
email=#{email} and
</if>
<!-- ognl会进行字符串与数字的转换判断 "0"==0 -->
<if test="gender==0 or gender==1">
gender=#{gender}
</if>
</trim>
</select>

<!-- public List<Employee> getEmpsByConditionChoose(Employee employee); -->
<select id="getEmpsByConditionChoose" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<where>
<!-- 如果带了id就用id查，如果带了lastName就用lastName查;只会进入其中一个 -->
<choose>
<when test="id!=null">
id=#{id}
</when>
<when test="lastName!=null">
last_name like #{lastName}
</when>
<when test="email!=null">
email = #{email}
</when>
<otherwise>
gender = 0
</otherwise>
</choose>
</where>
</select>

<!--public void updateEmp(Employee employee); -->
<update id="updateEmp">
<!-- Set标签的使用 -->
update tbl_employee
<set>
<if test="lastName!=null">
last_name=#{lastName}
</if>
<if test="email!=null">
email=#{email}
</if>
<if test="gender!=null">
gender=#{gender}
</if>
</set>
where id=#{id} </update>

<!--public void updateEmp(Employee employee); -->
<update id="updateEmp">
<!-- Set标签的使用 -->
update tbl_employee
<trim prefix="set" suffixOverrides=",">
<if test="lastName!=null">
last_name=#{lastName},
</if>
<if test="email!=null">
email=#{email},
</if>
<if test="gender!=null">
gender=#{gender}
</if>
</trim>
where id=#{id} -->
</update>