foreach遍历集合

• 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

• #{变量名}就能取出变量的值也就是当前遍历出的元素

• 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 index就是索引
  遍历map的时候index表示的就是map的key，item就是map的值

  public List<Employee> getEmpsByConditionForeach(@Param("ids") List<Integer> ids);

<!--    public List<Employee> getEmpsByConditionForeach(@Param("ids")List<Integer> employee);-->
<select id="getEmpsByConditionForeach" resultType="com.atguigu.mybatis.bean.Employee">select * from tb1_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listitem:将当前遍历出的元素赋值给指定的变量#{变量名}就能取出变量的值也就是当前遍历出的元素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 index就是索引遍历map的时候index表示的就是map的key，item就是map的值--><foreach collection="ids" item="item_id" separator="," open = "where id in (" close = ")">#{item_id}</foreach></select>

• 注意：这里的collection只能填list或者是map，如果想填ids，需要在参数上加@Param注解

    @Testpublic void test02() throws IOException {SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();SqlSession sqlSession = sqlSessionFactory.openSession();try{EmployeeMapperDynamicSQL mapper = sqlSession.getMapper(EmployeeMapperDynamicSQL.class);List<Employee> list = mapper.getEmpsByConditionForeach(Arrays.asList(1, 2, 3, 4));for (Employee emp : list){System.out.println(emp);}//手动提交数据sqlSession.commit();}finally {sqlSession.close();}}

foreach批量插入

• 方式一

  public void addEmps(@Param("emps") List<Employee> emps);

 <insert id="addEmps">INSERT INTO tb1_employee(last_name,email,gender,d_id)values<foreach collection="emps" item = "emp" separator=",">(#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})</foreach></insert>

 @Testpublic void test04() throws IOException {SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();SqlSession sqlSession = sqlSessionFactory.openSession();try{EmployeeMapperDynamicSQL mapper = sqlSession.getMapper(EmployeeMapperDynamicSQL.class);List<Employee> emps = new ArrayList<>();emps.add(new Employee(null,"smitdash","smitadsh@qq.com","1",new Department(1)));emps.add(new Employee(null,"allsadasen","allesadn@qq.com","0",new Department(1)));mapper.addEmps(emps);sqlSession.commit();}finally {sqlSession.close();}}

• 方式二
  这种方式需要数据库连接属性allowMultiQueries=true

dbconfig.properties:

jdbc.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&allowMultiQueries=true

 <insert id="addEmps"><foreach collection="emps" item = "emp" separator=";">INSERT INTO tb1_employee(last_name,email,gender,d_id)values(#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})</foreach></insert>