Common problems and solutions when MyBatis parameter type is String

1. Interpolation problem when the parameter is String

Suppose you have the following 1Dao interface method

public Account findByAccountType (String type)throws DaoException;

The corresponding Mapper xml

<select id="findByAccountType " parameterType="string" resultType="account">
  select *
  form account
  <where>
    <if test ="type != null">
      type=#{type}
    </if>
  </where>
</select>

1 Generally we write in this way, which is true for other types, but for String it throws the following exception:

There is no getter for property named 'type ' in 'class java.lang.String'

Because MyBatis requires that if the parameter is String, no matter what the parameter of the interface method is, the reference in ES21en.xml needs to be changed to _parameter to be recognized:

<select id="findByAccountType " parameterType="string" resultType="account">
  select *
  form account
  <where>
    <if test ="_parameter!= null">
      type=#{_parameter}
    </if>
  </where>
</select>

2. Comparing string parameters for equality

Error:

<if test="_parameter == '1' ">
  type=#{_parameter}
</if>

Correct:

<if test='_parameter == "1" '>
  type=#{_parameter}
</if>
<if test="_parameter == '1'.toString() ">
  type=#{_parameter}
</if>

Note: The above questions are not limited to < if > Tags, other dynamic sql tags have the same problem when processing String.