MyBatis Incoming Collection list array map parameter notation

The main use of foreach is in the build in condition, which can iterate a collection in an SQL statement. The properties of the Foreach element are mainly item,index,collection,open,separator,close. The item represents the alias of each element in the collection when it iterates, and index specifies a name that represents the position at which each iteration occurs during the iteration, and open indicates what the statement begins with, and separator indicates what symbol is used as the delimiter between each iteration. Close means the end, the most critical and error-prone when using foreach is the collection property, which must be specified, but in different cases the value of the property is not the same, there are 3 main cases:
If a single parameter is passed in and the parameter type is a list, the collection property value is list.

If a single parameter is passed in and the parameter type is an array, the value of the collection property is array.

If the parameters passed in are multiple, we need to encapsulate them into a map, of course, the single parameter can also be encapsulated as a map, in fact, if you pass in the parameter, in the MyBatis will also wrap it into a map, the map key is the parameter name, So this time the collection property value is the key to the incoming list or array object in its own encapsulated map.

Below we practice by code:

Data sheet:

Using Oracle's Hr.employees table

Entity: Employees

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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;}

Map file:

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<!--List:forech中的collection属性类型是List,collection的值必须是:list,item的值可以随意,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的值可以随意,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:不单单forech中的collection属性是map.key,其它所有属性都是map.key,比如下面的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>

Mapper class:

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publicinterfaceEmployeesMapper {   List<Employees> getEmployeesListParams(List<String> employeeIds);  List<Employees> getEmployeesArrayParams(String[] employeeIds);  List<Employees> getEmployeesMapParams(Map<String,Object> params);}

The above is a small series to introduce you to the MyBatis incoming collection list array map parameters of the whole narrative, I hope to help you!

MyBatis Incoming Collection list array map parameter notation