MyBatis 入门(七)--typeHandlers

一、作用及默认的处理

类型处理器的作用就是

• 查询时把数据库存储的值转换成java类型 
• 修改是把java类型转换成数据库类型存储，处理      

 下面这个表格描述了默认的类型处理器。 

类型处理器	Java 类型	JDBC 类型
BooleanTypeHandler	java.lang.Boolean, boolean	任何兼容的布尔值
ByteTypeHandler	java.lang.Byte, byte	任何兼容的数字或字节类型
ShortTypeHandler	java.lang.Short, short	任何兼容的数字或短整型
IntegerTypeHandler	java.lang.Integer, int	任何兼容的数字和整型
LongTypeHandler	java.lang.Long, long	任何兼容的数字或长整型
FloatTypeHandler	java.lang.Float, float	任何兼容的数字或单精度浮点型
DoubleTypeHandler	java.lang.Double, double	任何兼容的数字或双精度浮点型
BigDecimalTypeHandler	java.math.BigDecimal	任何兼容的数字或十进制小数类型
StringTypeHandler	java.lang.String	CHAR 和 VARCHAR 类型
ClobTypeHandler	java.lang.String	CLOB 和 LONGVARCHAR 类型
NStringTypeHandler	java.lang.String	NVARCHAR 和 NCHAR 类型
NClobTypeHandler	java.lang.String	NCLOB 类型
ByteArrayTypeHandler	byte[]	任何兼容的字节流类型
BlobTypeHandler	byte[]	BLOB 和 LONGVARBINARY 类型
DateTypeHandler	java.util.Date	TIMESTAMP 类型
DateOnlyTypeHandler	java.util.Date	DATE 类型
TimeOnlyTypeHandler	java.util.Date	TIME 类型
SqlTimestampTypeHandler	java.sql.Timestamp	TIMESTAMP 类型
SqlDateTypeHandler	java.sql.Date	DATE 类型
SqlTimeTypeHandler	java.sql.Time	TIME 类型
ObjectTypeHandler	Any	其他或未指定类型
EnumTypeHandler	Enumeration Type	VARCHAR-任何兼容的字符串类型, 作为代码存储(而不是索引)
EnumOrdinalTypeHandler	Enumeration Type	Any compatible NUMERIC or DOUBLE, as the position is stored (not the code itself).

二、自定义类型

       例如我们在数据库经常把时间存储为一个14位的VARCHAR（YYYYmmddssss）。而前台java层为java.util.Date,在这里我们就简单做一个类型处理。

• 定义类型处理                 

package com.elements.typehandler;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.Date;

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

public class DataTimeTypeHandler extends BaseTypeHandler<Date> {

    /**
     *
     * 这里应该是在保存数据的时候，把前台的日期类型转换成数据的varchar 我们使用了SimpleDateFormat来转换data类型
     * */
    @Override
    public void setNonNullParameter(PreparedStatement ps, int i,
            Date parameter, JdbcType jdbcType) throws SQLException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
        ps.setString(i, sdf.format(parameter));
    }

    /**
     * 下面三个函数应该都是返回到java层时调用，我们把varchar转换成Date类型
     */
    @Override
    public Date getNullableResult(ResultSet rs, String columnName)
            throws SQLException {
        String varchartime = rs.getString(columnName);
        if (varchartime!=null)
        return new Date(Long.parseLong(varchartime));
        else return null;
    }

    @Override
    public Date getNullableResult(ResultSet rs, int columnIndex)
            throws SQLException {
        String varchartime = rs.getString(columnIndex);
        if (varchartime!=null)
            return new Date(Long.parseLong(varchartime));
            else return null;
    }

    @Override
    public Date getNullableResult(CallableStatement cs, int columnIndex)
            throws SQLException {
        String varchartime = cs.getString(columnIndex);
        if (varchartime!=null)
            return new Date(Long.parseLong(varchartime));
            else return null;
    }

}

• mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "">

<configuration>

    <properties resource="jdbc.properties" />

  <typeHandlers>
     <typeHandler handler="com.elements.typehandler.DataTimeTypeHandler" javaType="java.util.Date" jdbcType="VARCHAR"/>
      <package name="com.elements.user"/>
  </typeHandlers>

    <environments default="dev">
        <environment id="dev">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="${driver}" />
                <property name="url" value="${url}" />
                <property name="username" value="${username}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>



    <mappers>
        <mapper class="com.elements.user.dao.UserMapper" />

    </mappers>

</configuration>

User类

package com.elements.user.model;

import java.util.Date;

public class User {
    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.userId
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private Integer userid;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.UserName
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private String username;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.UserEmail
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private String useremail;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.createTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private Date createtime;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.updateTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private Date updatetime;

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.userId
     *
     * @return the value of user.userId
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public Integer getUserid() {
        return userid;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.userId
     *
     * @param userid the value for user.userId
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setUserid(Integer userid) {
        this.userid = userid;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.UserName
     *
     * @return the value of user.UserName
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public String getUsername() {
        return username;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.UserName
     *
     * @param username the value for user.UserName
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setUsername(String username) {
        this.username = username == null ? null : username.trim();
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.UserEmail
     *
     * @return the value of user.UserEmail
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public String getUseremail() {
        return useremail;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.UserEmail
     *
     * @param useremail the value for user.UserEmail
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setUseremail(String useremail) {
        this.useremail = useremail == null ? null : useremail.trim();
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.createTime
     *
     * @return the value of user.createTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public Date getCreatetime() {
        return createtime;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.createTime
     *
     * @param createtime the value for user.createTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setCreatetime(Date createtime) {
        this.createtime = createtime ;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.updateTime
     *
     * @return the value of user.updateTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public Date getUpdatetime() {
        return updatetime;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.updateTime
     *
     * @param updatetime the value for user.updateTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setUpdatetime(Date updatetime) {
        this.updatetime = updatetime;
    }

    @Override
    public String toString() {
        return "User [userid=" + userid + ", username=" + username
                + ", useremail=" + useremail + ", createtime=" + createtime
                + ", updatetime=" + updatetime + "]";
    }


}

• UserMapper配置文件

• <?xml version="1.0" encoding="UTF-8" ?>
  <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "" >
  <mapper namespace="com.elements.user.dao.UserMapper" >
  
  
    <resultMap id="BaseResultMap" type="com.elements.user.model.User" >
  
      <!--
        WARNING - @mbggenerated
        This element is automatically generated by MyBatis Generator, do not modify.
        This element was generated on Wed Apr 27 15:05:09 CST 2016.
      -->
      <id column="userId" property="userid" jdbcType="INTEGER" />
      <result column="UserName" property="username" jdbcType="VARCHAR" />
      <result column="UserEmail" property="useremail" jdbcType="VARCHAR" />
      <result column="createTime" property="createtime" jdbcType="VARCHAR" />
      <result column="updateTime" property="updatetime" jdbcType="VARCHAR" />
    </resultMap>
    <sql id="Base_Column_List" >
      <!--
        WARNING - @mbggenerated
        This element is automatically generated by MyBatis Generator, do not modify.
        This element was generated on Wed Apr 27 15:05:09 CST 2016.
      -->
      userId, UserName, UserEmail, createTime, updateTime
    </sql>
  
    <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
      <!--
        WARNING - @mbggenerated
        This element is automatically generated by MyBatis Generator, do not modify.
        This element was generated on Wed Apr 27 15:05:09 CST 2016.
      -->
      select
      <include refid="Base_Column_List" />
      from user
      where userId = #{userid,jdbcType=INTEGER}
    </select>
  
    <insert id="insert" parameterType="com.elements.user.model.User" >
      <!--
        WARNING - @mbggenerated
        This element is automatically generated by MyBatis Generator, do not modify.
        This element was generated on Wed Apr 27 15:05:09 CST 2016.
      -->
      insert into user (userId, UserName, UserEmail,
        createTime, updateTime)
      values (#{userid,jdbcType=INTEGER}, #{username,jdbcType=VARCHAR}, #{useremail,jdbcType=VARCHAR},
        #{createtime,jdbcType=VARCHAR}, #{updatetime,jdbcType=VARCHAR})
    </insert>
  
  
  </mapper>

注意：我们没有在mapper文件内显示的做类型转换  ，他已经默认把这两种类型（javaType="java.util.Date" jdbcType="VARCHAR" ）的互转都调用我们的类型处理了                                                                           

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