mybatis 处理枚举类型

mybatis支持持久化enum类型属性。假设t_user表中有一列gender（性别）类型为 varchar2(10)，存储 male 或者 female 两种值。并且，user对象有一个enum类型的gender 属性，如下所示：

public enum gender { 
male,female; 
}

 

默认情况下mybatis使用enumtypehandler来处理enum类型的java属性，并且将其存储为enum值的名称。我们不需要为此做任何额外的配置。可以像使用基本数据类型属性一样使用enum类型属性，如下：

create table t_user(
          id number primary key,
          name varchar2(50),
          gender varchar2(10)
);

 

public class user{ 
            private integer id; 
            private string name; 
            private gender gender; 

            //setters and getters 
} 

 映射文件：

<insert id="insertuser" parametertype="user"> 
    <selectkey keyproperty="id" resulttype="int" order="before">
        select my_seq.nextval from dual
    </selectkey>
    insert into t_user(id,name,gender) 
    values(#{id},#{name},#{gender}) 
</insert>

映射接口：

public interface xxxxmapper{
    int insertuser(user user);    
}

测试方法：

@test
public void test_insertuser(){

sqlsession sqlsession = null;
try {
sqlsession = mybatissqlsessionfactory.opensession();

specialmapper mapper = sqlsession.getmapper(specialmapper.class);
user user = new user("tom",gender.male);

mapper.insertuser(user);

sqlsession.commit();
} catch (exception e) {
e.printstacktrace();
}
}

 

当执行insertstudent语句的时候mybatis会取gender枚举（female/male）的名称，存储到gender列中。

如果你想存储female为0，male为1到gender列中，需要在mybatis-config.xml文件中配置专门的类型处理器，并指定它处理的枚举类型是哪个。
<typehandler handler="org.apache.ibatis.type.enumordinaltypehandler" javatype="com.briup.special.gender"/>

enumordinaltypehandler这是个类型处理器，源码中有个set方法就是在帮助我们存值，源码如下

/**
 *    copyright 2009-2017 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.callablestatement;
import java.sql.preparedstatement;
import java.sql.resultset;
import java.sql.sqlexception;

/**
 * @author clinton begin
 */
public class enumordinaltypehandler<e extends enum<e>> extends basetypehandler<e> {

  private final class<e> type;
  private final e[] enums;

  public enumordinaltypehandler(class<e> type) {
    if (type == null) {
      throw new illegalargumentexception("type argument cannot be null");
    }
    this.type = type;
    this.enums = type.getenumconstants();
    if (this.enums == null) {
      throw new illegalargumentexception(type.getsimplename() + " does not represent an enum type.");
    }
  }

  @override
  public void setnonnullparameter(preparedstatement ps, int i, e parameter, jdbctype jdbctype) throws sqlexception {
    ps.setint(i, parameter.ordinal());
  }

  @override
  public e getnullableresult(resultset rs, string columnname) throws sqlexception {
    int i = rs.getint(columnname);
    if (rs.wasnull()) {
      return null;
    } else {
      try {
        return enums[i];
      } catch (exception ex) {
        throw new illegalargumentexception("cannot convert " + i + " to " + type.getsimplename() + " by ordinal value.", ex);
      }
    }
  }

  @override
  public e getnullableresult(resultset rs, int columnindex) throws sqlexception {
    int i = rs.getint(columnindex);
    if (rs.wasnull()) {
      return null;
    } else {
      try {
        return enums[i];
      } catch (exception ex) {
        throw new illegalargumentexception("cannot convert " + i + " to " + type.getsimplename() + " by ordinal value.", ex);
      }
    }
  }

  @override
  public e getnullableresult(callablestatement cs, int columnindex) throws sqlexception {
    int i = cs.getint(columnindex);
    if (cs.wasnull()) {
      return null;
    } else {
      try {
        return enums[i];
      } catch (exception ex) {
        throw new illegalargumentexception("cannot convert " + i + " to " + type.getsimplename() + " by ordinal value.", ex);
      }
    }
  }
  
}

枚举类型的【顺序值】是根据enum中的声明顺序赋值的。如果改变了gender里面对象的声明顺序，则数据库存储的数据和此顺序值就不匹配了。