mybatis - Java中类型与数据库mysql、oracle等的对应关系

      在使用mybatis时，会在maper.xml文件中写对应mapper接口类的sql语句，里面会有涉及到Java中类型与数据库mysql、oracle等的对应关系，事实上在mybatis包中有一个名为JdbcType的枚举类，下面记录一下这个枚举类的详情，这样方便开发，感兴趣的可以了解一下。

pom

<!-- https://mvnrepository.com/artifact/tk.mybatis/mapper-spring-boot-starter -->
<dependency>
    <groupId>tk.mybatis</groupId>
    <artifactId>mapper-spring-boot-starter</artifactId>
    <version>2.1.5</version>
</dependency>

/**
 *    Copyright 2009-2018 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.type;

import java.sql.Types;
import java.util.HashMap;
import java.util.Map;

/**
 * @author Clinton Begin
 */
public enum JdbcType {
  /*
   * This is added to enable basic support for the
   * ARRAY data type - but a custom type handler is still required
   */
  ARRAY(Types.ARRAY),
  BIT(Types.BIT),
  TINYINT(Types.TINYINT),
  SMALLINT(Types.SMALLINT),
  INTEGER(Types.INTEGER),
  BIGINT(Types.BIGINT),
  FLOAT(Types.FLOAT),
  REAL(Types.REAL),
  DOUBLE(Types.DOUBLE),
  NUMERIC(Types.NUMERIC),
  DECIMAL(Types.DECIMAL),
  CHAR(Types.CHAR),
  VARCHAR(Types.VARCHAR),
  LONGVARCHAR(Types.LONGVARCHAR),
  DATE(Types.DATE),
  TIME(Types.TIME),
  TIMESTAMP(Types.TIMESTAMP),
  BINARY(Types.BINARY),
  VARBINARY(Types.VARBINARY),
  LONGVARBINARY(Types.LONGVARBINARY),
  NULL(Types.NULL),
  OTHER(Types.OTHER),
  BLOB(Types.BLOB),
  CLOB(Types.CLOB),
  BOOLEAN(Types.BOOLEAN),
  CURSOR(-10), // Oracle
  UNDEFINED(Integer.MIN_VALUE + 1000),
  NVARCHAR(Types.NVARCHAR), // JDK6
  NCHAR(Types.NCHAR), // JDK6
  NCLOB(Types.NCLOB), // JDK6
  STRUCT(Types.STRUCT),
  JAVA_OBJECT(Types.JAVA_OBJECT),
  DISTINCT(Types.DISTINCT),
  REF(Types.REF),
  DATALINK(Types.DATALINK),
  ROWID(Types.ROWID), // JDK6
  LONGNVARCHAR(Types.LONGNVARCHAR), // JDK6
  SQLXML(Types.SQLXML), // JDK6
  DATETIMEOFFSET(-155), // SQL Server 2008
  TIME_WITH_TIMEZONE(Types.TIME_WITH_TIMEZONE), // JDBC 4.2 JDK8
  TIMESTAMP_WITH_TIMEZONE(Types.TIMESTAMP_WITH_TIMEZONE); // JDBC 4.2 JDK8

  public final int TYPE_CODE;
  private static Map<Integer,JdbcType> codeLookup = new HashMap<>();

  static {
    for (JdbcType type : JdbcType.values()) {
      codeLookup.put(type.TYPE_CODE, type);
    }
  }

  JdbcType(int code) {
    this.TYPE_CODE = code;
  }

  public static JdbcType forCode(int code)  {
    return codeLookup.get(code);
  }

}