Mybatis中如何使用动态SQL比较MySQL二进制UUID

Question

We store one of the UUID values as binary(16) in mysql db.

spec

 MyTable myTable = new MyTable();` //table
 SqlColumn<Long> id = column("id");` // id column
 SqlColumn<UUID> myUuidColumn = column("my_uuid");` //uuid column

Dynamic sql query for select.

            select(myTable.id)
                .from(myTable)
                .where(myTable.myUuidColumn, isEqualTo(UUID.fromString("e59bf2fd-e742-4314-ab02-db195e0168c8")))
                .build()
                .render(RenderingStrategies.MYBATIS3);

But this is not working, probably due to UUID is not being natively supported. How to fix this other than changing the mapper to use plain sql query?

Answer 1

You need to write a custom type handler.
The implementation depends on the driver and/or the column type.
Here is the type handler implementation for your usage (ie BINARY(16) ).

import java.nio.ByteBuffer;
import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.UUID;

import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.MappedJdbcTypes;

@MappedJdbcTypes(JdbcType.BINARY)
public class UuidTypeHandler extends BaseTypeHandler<UUID> {
  @Override
  public void setNonNullParameter(PreparedStatement ps, int i, UUID parameter, JdbcType jdbcType) throws SQLException {
    ps.setBytes(i, uuidToBytes(parameter));
  }

  private static byte[] uuidToBytes(UUID uuid) {
    ByteBuffer bb = ByteBuffer.wrap(new byte[16]);
    bb.putLong(uuid.getMostSignificantBits());
    bb.putLong(uuid.getLeastSignificantBits());
    return bb.array();
  }

  @Override
  public UUID getNullableResult(ResultSet rs, String columnName) throws SQLException {
    return bytesToUuid(rs.getBytes(columnName));
  }

  @Override
  public UUID getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
    return bytesToUuid(rs.getBytes(columnIndex));
  }

  @Override
  public UUID getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
    return bytesToUuid(cs.getBytes(columnIndex));
  }

  private static UUID bytesToUuid(byte[] bytes) {
    if (bytes == null) {
      return null;
    }
    ByteBuffer byteBuffer = ByteBuffer.wrap(bytes);
    Long high = byteBuffer.getLong();
    Long low = byteBuffer.getLong();
    return new UUID(high, low);
  }
}

To register the type handler globally...

• if you are using mybatis-spring-boot , specify mybatis.type-handlers-package in your application.properties .
• if you are not using spring-boot, set typeHandlersPackage or typeHandlers property of SqlSessionFactoryBean .

If, for some reason, you cannot register the type handler globally, you may have to pass the fully-qualified-name of the type handler when initializing the SqlColumn<UUID> myUuidColumn .