【MyBatis】动态SQL示例

标签：语句   class   选择   动态sql   引用   写代码   test   property   返回   

【MyBatis】配置文件示例
【MyBatis】映射文件示例

DAO文件

EmployeeMapperDynamicSQL.java

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);

}

映射文件

EmployeeMapperDynamicSQL.xml MyBatis动态SQL主要包括if、choose、trim、foreach

<?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>

Bean

参见下面中的Bean小节

【MyBatis】映射文件示例

测试类

MyBatisTest.java

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.setLastName("%e%");
            List<Employee> list = mapper.getEmpsTestInnerParameter(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();
        }
    }   
    
}

【MyBatis】动态SQL示例

标签：语句   class   选择   动态sql   引用   写代码   test   property   返回   

原文地址：https://www.cnblogs.com/z00377750/p/12397622.html