MyBatis参数传入集合之foreach动态sql

foreach的主要用在构建in条件中，它能够在SQL语句中进行迭代一个集合。foreach元素的属性主要有item，index，collection，open，separator，close。item表示集合中每个元素进行迭代时的别名，index指定一个名字，用于表示在迭代过程当中，每次迭代到的位置，open表示该语句以什么开始，separator表示在每次进行迭代之间以什么符号做为分隔符，close表示以什么结束，在使用foreach的时候最关键的也是最容易出错的就是collection属性，该属性是必须指定的，可是在不一样状况下，该属性的值是不同的，主要有一下3种状况： 

1. 若是传入的是单参数且参数类型是一个List的时候，collection属性值为list .
2. 若是传入的是单参数且参数类型是一个array数组的时候，collection的属性值为array .
3. 若是传入的参数是多个的时候，咱们就须要把它们封装成一个Map了，固然单参数也能够封装成map，实际上若是你在传入参数的时候，在MyBatis里面也是会把它封装成一个Map的，map的key就是参数名，因此这个时候collection属性值就是传入的List或array对象在本身封装的map里面的key.

下面咱们经过代码实践:

 

数据表:

采用Oracle的HR.Employees表

        实体:Employees

public class Employees {
    private Integer employeeId;
    private String firstName;
    private String lastName;
    private String email;
    private String phoneNumber;
    private Date hireDate;
    private String jobId;
    private BigDecimal salary;
    private BigDecimal commissionPct;
    private Integer managerId;
    private Short departmentId;
}  
映射文件:

    <!--List:forech中的collection属性类型是List,collection的值必须是:list,item的值能够随意,Dao接口中参数名字随意 -->
    <select id="getEmployeesListParams" resultType="Employees">
        select *
        from EMPLOYEES e
        where e.EMPLOYEE_ID in
        <foreach collection="list" item="employeeId" index="index"
            open="(" close=")" separator=",">
            #{employeeId}
        </foreach>
    </select>

    <!--Array:forech中的collection属性类型是array,collection的值必须是:list,item的值能够随意,Dao接口中参数名字随意 -->
    <select id="getEmployeesArrayParams" resultType="Employees">
        select *
        from EMPLOYEES e
        where e.EMPLOYEE_ID in
        <foreach collection="array" item="employeeId" index="index"
            open="(" close=")" separator=",">
            #{employeeId}
        </foreach>
    </select>

    <!--Map:不仅仅forech中的collection属性是map.key,其它全部属性都是map.key,好比下面的departmentId -->
    <select id="getEmployeesMapParams" resultType="Employees">
        select *
        from EMPLOYEES e
        <where>
            <if test="departmentId!=null and departmentId!=''">
                e.DEPARTMENT_ID=#{departmentId}
            </if>
            <if test="employeeIdsArray!=null and employeeIdsArray.length!=0">
                AND e.EMPLOYEE_ID in
                <foreach collection="employeeIdsArray" item="employeeId"
                    index="index" open="(" close=")" separator=",">
                    #{employeeId}
                </foreach>
            </if>
        </where>
    </select>

 

判断能够用

<choose>
<when test="null!=list and list.size!=0">
AND OI.ORDER_NO IN
<foreach collection="list" item="orderNo" index="index"
open="(" separator="," close=")">
#{orderNo}
</foreach>
</when>
<otherwise>
AND 1 != 1
</otherwise>
</choose>

Mapper类:
public interface EmployeesMapper { 

    List<Employees> getEmployeesListParams(List<String> employeeIds);

    List<Employees> getEmployeesArrayParams(String[] employeeIds);

    List<Employees> getEmployeesMapParams(Map<String,Object> params);
}

测试方法(未贴完整代码):

    @Test      public void testGetEmployeesListParams() {         List<String> employeeIds = Arrays.asList("100", "101", "200");         List<Employees> result = employeesMapper                 .getEmployeesListParams(employeeIds);         assertEquals(3, result.size());     }     @Test     public void testGetEmployeesArrayParams() {         String[] employeeIds = new String[] { "100", "200" };         List<Employees> result = employeesMapper                 .getEmployeesArrayParams(employeeIds);         assertEquals(2, result.size());     }     @Test     public void testGetEmployeesMapParams() {         String departmentId = "60";         List<String> employeeIdsList = Arrays.asList("103", "104", "105");         String[] employeeIdsArray = new String[] { "103", "104" };         // 传入多个参数         Map<String, Object> params = new HashMap<String, Object>();         params.put("departmentId", departmentId);         params.put("employeeIdsList", employeeIdsList);         params.put("employeeIdsArray", employeeIdsArray);         List<Employees> result = employeesMapper.getEmployeesMapParams(params);         assertEquals(3, result.size());     }