How to configure one-to-many and many-to-one relationsh…

1 year ago
Noah Thompson
2 minutes

The configuration of one-to-many and many-to-one relationships in MyBatis requires the use of two tags: and .

The steps for configuring a one-to-many relationship are as follows:

  1. Create two entities, one representing the one side and the other representing the many side.
  2. In one side’s entity class, include a collection property to store multiple entity objects from the other side.
  3. selection
  4. assortment
  5. real estate
  6. type of
  7. choose
  8. Assortment or group of items.
  9. Choose

The steps for configuring a one-to-many relationship are as follows:

  1. Create two entity classes, one representing the many side and the other representing the one side.
  2. Add an entity object property in the class of the one with the many side to store an entity object of the one side.
  3. – Organization
  4. – organization
  5. real estate
  6. Type of Java programming language
  7. column – a vertical structure used for support or decoration in a building
  8. –
  9. choose

Example setup:

Example of configuring a one-to-many relationship:

<resultMap id="userMap" type="User">
  <id property="id" column="id"/>
  <result property="name" column="name"/>
  <collection property="orders" ofType="Order" select="getOrdersByUserId" column="id"/>
</resultMap>

<select id="getUserById" parameterType="int" resultMap="userMap">
  SELECT * FROM user WHERE id = #{id}
</select>

<select id="getOrdersByUserId" parameterType="int" resultMap="orderMap">
  SELECT * FROM orders WHERE user_id = #{userId}
</select>

Example of configuring a one-to-many relationship:

<resultMap id="orderMap" type="Order">
  <id property="id" column="id"/>
  <result property="name" column="name"/>
  <association property="user" javaType="User" column="user_id" select="getUserById"/>
</resultMap>

<select id="getOrderById" parameterType="int" resultMap="orderMap">
  SELECT * FROM orders WHERE id = #{id}
</select>

<select id="getUserById" parameterType="int" resultMap="userMap">
  SELECT * FROM user WHERE id = #{id}
</select>

These examples assume there are two tables: user and orders, where the foreign key column in the orders table is user_id.

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