mybatis 自定义枚举转换类

    最近在搭建maven多模块项目： http://git.oschina.net/alexgaoyh/MutiModule-parent

    项目整体代码部分在上文链接的git中，下面的代码段落只是部分个人觉得比较重要的段落

    在选择持久化DAO部分的时候，选择了mybatis，实体中变量的定义，想来来使用Enum代替常量的某些好处。所以才有下文的这些功能：

package com.alexgaoyh.MutiModule.domain;

import java.io.Serializable;

import com.alexgaoyh.MutiModule.domain.enumState.DeleteFlagState;

public class BaseEntity implements Serializable{

	/**
	 * 
	 */
	private static final long serialVersionUID = 997102449095543774L;

	/**
	 * 编号，主键标示
	 */
	private Integer id;
	
	/**
	 * 是否删除状态
	 */
	private DeleteFlagState deleteFlagState = DeleteFlagState.NO;

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public DeleteFlagState getDeleteFlagState() {
		return deleteFlagState;
	}

	public void setDeleteFlagState(DeleteFlagState deleteFlagState) {
		this.deleteFlagState = deleteFlagState;
	}
}

package com.alexgaoyh.MutiModule.persist.handler;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

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

import com.alexgaoyh.MutiModule.domain.enumState.DeleteFlagState;

/**
 * 自定义DeleteFlagState转换类 <br>
 * 存储属性：DeleteFlagState.getCode() <br>
 */
public class DeleteFlagStateHandler extends BaseTypeHandler<DeleteFlagState> {
 
    private Class<DeleteFlagState> type;
 
    private final DeleteFlagState[] enums;
 
    /**
     * 设置配置文件设置的转换类以及枚举类内容，供其他方法更便捷高效的实现
     * @param type 配置文件中设置的转换类
     */
    public DeleteFlagStateHandler(Class<DeleteFlagState> 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 DeleteFlagState getNullableResult(ResultSet rs, String columnName) throws SQLException {
        // 根据数据库存储类型决定获取类型，本例子中数据库中存放INT类型
        int i = rs.getInt(columnName);
         
        if (rs.wasNull()) {
            return null;
        } else {
            // 根据数据库中的code值，定位DeleteFlagState子类
            return locateDeleteFlagState(i);
        }
    }
 
    @Override
    public DeleteFlagState getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        // 根据数据库存储类型决定获取类型，本例子中数据库中存放INT类型
        int i = rs.getInt(columnIndex);
        if (rs.wasNull()) {
            return null;
        } else {
            // 根据数据库中的code值，定位DeleteFlagState子类
            return locateDeleteFlagState(i);
        }
    }
 
    @Override
    public DeleteFlagState getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        // 根据数据库存储类型决定获取类型，本例子中数据库中存放INT类型
        int i = cs.getInt(columnIndex);
        if (cs.wasNull()) {
            return null;
        } else {
            // 根据数据库中的code值，定位DeleteFlagState子类
            return locateDeleteFlagState(i);
        }
    }
 
    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, DeleteFlagState parameter, JdbcType jdbcType)
            throws SQLException {
        // baseTypeHandler已经帮我们做了parameter的null判断
        ps.setInt(i, parameter.getCode());
 
    }
     
    /**
     * 枚举类型转换，由于构造函数获取了枚举的子类enums，让遍历更加高效快捷
     * @param code 数据库中存储的自定义code属性
     * @return code对应的枚举类
     */
    private DeleteFlagState locateDeleteFlagState(int code) {
        for(DeleteFlagState status : enums) {
            if(status.getCode().equals(Integer.valueOf(code))) {
                return status;
            }
        }
        throw new IllegalArgumentException("未知的枚举类型：" + code + ",请核对" + type.getSimpleName());
    }
 
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
	 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
	 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
	
<!-- namespace 必须是DemoMapper接口的路径 --> 
<mapper namespace="com.alexgaoyh.MutiModule.persist.demo.DemoMapper">

	<resultMap type="Demo" id="DemoResultMap">
		<id column="id" property="id"/>
		<result column="name" property="name"/>
		<result column="deleteFlagState" property="deleteFlagState" typeHandler="com.alexgaoyh.MutiModule.persist.handler.DeleteFlagStateHandler"/>
	</resultMap>
	
	<insert id="insertDemo" parameterType="Demo">
		insert into Demo(deleteFlagState, name) 
		values(
		#{deleteFlagState, typeHandler=com.alexgaoyh.MutiModule.persist.handler.DeleteFlagStateHandler},
		#{name})
	</insert>
	
	<select id="selectDemoById" resultMap="DemoResultMap" parameterType="java.lang.Integer">
		select * from Demo where id=#{id}
	</select>
	
</mapper>

mybatis 自定义枚举转换类

原文：http://my.oschina.net/alexgaoyh/blog/401743