Mybatis type of processor

Processor type (type converter)
1.MyBatis some common type of processor comes
int - number

2. Custom Types processor MyBatis

java <=> database (jdbc type)
Example:
the entity class has member variables Student representative of M boolean stuSex true false means female
table studen in t: number stuSex 1: 0 Male: Female

Custom type converter (boolean <=> number) steps of:

1. Creating converter: TypeHandler need to implement the interface
   by reading the source code was found, there is a class that implements this interface BaseTypeHandler, so to achieve converters have two options:
   . I implement the interface TypeHandler interfaces
   . Ii inherited BaseTypeHandler

get & set :

package org.lanqiao.converter;

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;

//BaseTypeHandler<java类型>
public class BooleanAndIntConverter extends BaseTypeHandler<Boolean>{//这里要加上泛型

	
	/*
	 * 下面的参数中:
	 * ps:PreparedStatement对象
	 * i：PreparedStatement对象操作参数的位置
	 * parameter:java值
	 * jdbcType：jdbc操作的数据库类型
	 */
	 //java代码(boolean)-DB类型(number)
	@Override
	public void setNonNullParameter(PreparedStatement ps, int i, Boolean parameter, JdbcType jdbcType)
			throws SQLException {
			if(parameter) {//1
				ps.setInt(i, 1); 
			}else {//0
				ps.setInt(i, 0); 
			}
	}

	//db数据库类型(number)->java类型(boolean)
	@Override
	public Boolean getNullableResult(ResultSet rs, String columnName) throws SQLException {
		int sexNum = rs.getInt(columnName) ;//rs.getInt("stuno") ;
		return sexNum == 1?true:false ;
	}

	@Override
	public Boolean getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
		int sexNum = rs.getInt(columnIndex) ;//rs.getInt(1)
		return sexNum == 1?true:false ;
	}

	@Override
	public Boolean getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
		int sexNum = cs.getInt(columnIndex) ;//rs.getInt(1)
		return sexNum == 1?true:false ;
	}
}

You can see it get overloaded three ways:

	//通过resultSet & 列名
	public Boolean getNullableResult(ResultSet rs, String columnName) 
	//通过resultSet & 下标
	public Boolean getNullableResult(ResultSet rs, int columnIndex) 
	//通过结果集拿
	public Boolean getNullableResult(CallableStatement cs, int columnIndex)

2. Configuration conf.xml

<typeHandlers>
		<typeHandler handler="org.lanqiao.converter.BooleanAndIntConverter" javaType="Boolean" jdbcType="INTEGER" />
	</typeHandlers>

resultMap

resultMap can be used to solve the types of problems
are mainly two:

1. Java type and database type are not the same, such as the above boolean false and not interconversion
2. For example, the entity class Student.java There is a field StudentNumber, the database is the number, this is not matched
   both cases we can use resultMap, other cases (such as a.String and varchar2 direct identification) directly on resultType can

<select id="queryStudentByStuno" 	parameterType="int"  	resultMap="studentMapping" >
		select * from student where stuno = #{stuno}
</select>
<!--注意这里的stuSex涉及到类型转换,要在大括号里写上javaType&jdbcType-->
<insert id="addStudentWithConverter" parameterType="student" >
		insert into student(stuno,stuname,stuage,graname,stusex) values(#{stuNo},#{stuName},#{stuAge},#{graName} ,#{stuSex ,javaType=boolean  ,jdbcType=INTEGER   } ) 
</insert>	
	
	<resultMap type="student" id="studentMapping">
			<!-- 分为主键id 和非主键 result-->
			<id property="id"  column="stuno"  /><!--主键用id-->
			<!--别的用property-->
			<result property="studentName"  column="name" />
			<result property="studentAge"  column="age" />
			<result property="studentName"  column="name" />
			<!--这里有类型转换,在后面加上javaType和jdbcType就可以-->
			<result property="studentSex"  column="stusex"  javaType="boolean" jdbcType="INTEGER"/>
	</resultMap>

Requires attention to the problem:

insert into student(stuno,stuname,stuage,graname,stusex) values(#{stuNo},#{stuName},#{stuAge},#{graName} ,#{stuSex ,javaType=boolean  ,jdbcType=INTEGER   } ) 

Note # {stuNo} is stored in the property value, the need for strict case-sensitive.
focusky
the commit applied CRUD