mybatis 一对一与一对多collection和association的使用

前言

在mybatis如何进行一对一、一对多的多表查询呢？这里用一个简单的例子说明。

一对一

association

association通常用来映射一对一的关系，例如，有个类 PointTypeName,对应的实体类如下：(getter,setter方法省略)

import java.util.List;

public class PointTypeName{
	
	private static final long serialVersionUID = 1L;
	private Integer typeName;

}

有个类 PointsConsump,对应的实体类如下：

import java.sql.Timestamp;

public class PointsConsump {

	private Long key;
	private Integer levelKey;
	private Integer typeName;
	private Integer consumption;
	private Integer ticket;
	private Integer chance;
	private Timestamp reduceAt;
	private Timestamp updatedAt;
	private Integer version;
	private String level;
	
}

如果我想查询一个 PointsConsump 的时候，也查到 PointsConsump，可以怎样写呢？在类 PointsConsump 加入一个属性 PointsConsump

import java.util.List;

public class PointTypeName{
	
	private static final long serialVersionUID = 1L;
	private Integer typeName;
	private PointsConsump pointsConsump;

}

mapper.xml 我在 PointsConsump 类的 mapper.xml 这样配置（这里一般用id或者key我的表比较特殊）

<resultMap type="hotkidclub.model.points.PointTypeName"
		id="pointsMap">
		<id column="typeName" property="typeName" />
		<association property="pointsConsump" ofType="hotkidclub.model.points.PointsConsump">
			<id property="key" column="key" />
			<result property="level" column="level" />
			<result property="consumption" column="consumption" />
			<result property="ticket" column="ticket" />
			<result property="chance" column="chance" />
		</association>
	</resultMap>

一对多，collection，理解了一对一，一对多容易理解。

实体类增加对应属性

import java.util.List;

public class PointTypeName{
	
	private static final long serialVersionUID = 1L;
	private Integer typeName;
	private List<PointsConsump> pointsConsump;

}

mapper.xml 我在 PointsConsump 类的 mapper.xml 这样配置（这里一般用id或者key我的表比较特殊）

<resultMap type="hotkidclub.model.points.PointTypeName" id="pointsMap">
        <id column="typeName" property="typeName" />
		<collection property="pointsConsump" ofType="hotkidclub.model.points.PointsConsump">
        	<id property="key" column="key"/>
        	<result property="level" column="level"/>
        	<result property="consumption" column="consumption"/>
        	<result property="ticket" column="ticket"/>
        	<result property="chance" column="chance"/>
    	</collection>
    </resultMap>