CRUD Operations

Select

<select id="findAll" resultType="Customer">
  SELECT * FROM customers ORDER BY id
</select>

Insert With Generated Keys

<insert id="insert" useGeneratedKeys="true" keyProperty="id">
  INSERT INTO customers (name, email, city)
  VALUES (#{name}, #{email}, #{city})
</insert>

useGeneratedKeys + keyProperty writes the auto-generated key back into the Java object (Customer.getId() returns it).

Update and Delete

<update id="update">
  UPDATE customers
  SET name = #{name}, email = #{email}, city = #{city}
  WHERE id = #{id}
</update>

<delete id="delete">
  DELETE FROM customers WHERE id = #{id}
</delete>

Returning the Affected Count

UPDATE and DELETE statements return the number of rows changed. Return int from the mapper method to read it:

int rows = mapper.update(customer);   // 1 when a row was updated

Full CRUD Example

CustomerMapper mapper = session.getMapper(CustomerMapper.class);
mapper.insert(new Customer("Priya", "priya@example.com", "Mumbai"));
Customer c = mapper.findById(c.getId());
c.setCity("Pune");
mapper.update(c);
int deleted = mapper.delete(c.getId());

Key Points

• Select, insert, update, delete map to the four mapper statement tags.
• useGeneratedKeys retrieves auto-increment IDs into the entity.
• Updates/deletes return the number of affected rows.
• #{} parameters are always bound safely.