Mybatis Usage Details

Mybatis Usage Details

1. mybatis encapsulates the results after SQL Execution. If no record is returned, only the encapsulated object has no value, and the object is not null;

(This problem has been neglected twice. when judging the returned Array results, I use if (Array! = Null) the result is correct. It should be if (Array. length! = 0) Determine whether the record is null)

 

2. In the mapper xml file, if <test = "ids. length! = 0 and ids! = Null "> here the and operation is used.

 

3. Data Binding

The input parameter is an integer array. The parameter in the collection is "array" and cannot be another value.

<Select id = "findSelectedItemsList" parameterType = "Integer []" resultType = "ItemsCustom"> select * from item <where> <! -- Pass the array --> <if test = "array! = Null "> <foreach collection =" array "index =" index "item =" item "open =" and id in ("separator =", "close = ") ">#{ item} </foreach> </if> </where> </select>

If the object is a pojo object with an array attribute ids, the collection parameter must be the attribute variable ids.

<insert id="createRelation" parameterType="com.xidian.ssm.po.Relation">   <if test="ids.length!=0 and ids!=null">        <foreach close="" collection="ids" index="index" item="ref_id" open="" separator=";">             insert into relation (id,ref_id) value(#{id,jdbcType=INTEGER},#{ref_id,jdbcType=INTEGER})         </foreach>    </if></insert>