今天進行了一個嘗試，嘗試背景是：

先設定了一個Goods類，裡面存在屬性price，

但是，我現在要進行範圍查詢，也就是price > ? and price < ?,但是，如果在向statement傳入Goods這個實體類時，只能給一個price賦值，而標籤卻要寫兩個if進行判斷。下面進行程式碼示例：

Goods類的屬性資訊：類中包含get、set方法，此處沒有複製。

public class Goods {	
	private int id;
	private String name;
	private String description;
	private double price;
 

mapper.xml檔案

<mapper namespace="Goods">
	<select id="selByCondition4if" resultType="com.test.pojo.Goods">
		select * from TestMybatis
		<where>
			<if test="id > 0">
				and id = #{id}
			</if>
			<if test="name != null and name.trim().length() > 0">
				and name like '%'||#{name}||'%'
			</if>
			<if test="description != null and description.trim().length() > 0">
				and description like '%'||#{description}||'%'
			</if>
			<if test="price > 0">
				                    and price > #{price}
			                </if>
			                <if test="price2 > 0">
			                        	and price < #{price2}
		                	</if>
 

		</where>
	</select>
</mapper>

為了解決這個問題，我新增加了一個類叫做GoodsModel.java，並讓該類繼承Goods類,裡面只有一個屬性是price2,並生成get、set方法。

public class GoodsModel extends Goods{

	private double price2;

	public double getPrice2() {
		return price2;
	}

	public void setPrice2(double price2) {
		this.price2 = price2;
	}		
}
 

這樣就可以對mapper.xml檔案傳入GoodsModel的物件，這樣就不僅包含了Goods的所有屬性，還包含了範圍查詢的另一個price的值，下面是測試程式碼：

public class TestApp {

	public static void main(String[] args) throws Exception {
		SqlSession sqlSession = SqlSessionUtil.getSqlSession();
		GoodsModel goodsModel = new GoodsModel();		
		goodsModel.setId(1);
		goodsModel.setName("c");
		goodsModel.setDescription("c");
		goodsModel.setPrice(2d);
		goodsModel.setPrice2(5d);
		List<Goods> list = sqlSession.selectList("Goods.selByCondition4if", goodsModel);
		System.out.println(list);
		sqlSession.close();	
	}
}

這樣就可以得到結果了，控制檯輸出為

DEBUG [main] - ==>  Preparing: select * from TestMybatis WHERE id = ? and name like '%'||?||'%' and description like '%'||?||'%' and price > ? and price < ? 
DEBUG [main] - ==> Parameters: 1(Integer), c(String), c(String), 2.0(Double), 5.0(Double)
DEBUG [main] - <==      Total: 1
[Goods [id=1, name=cathy, description=cathyy, price=3.0]]

 <if test="price2 > 0">
	    and price < #{price2}
</if>

是否還會生效，於是測試程式碼就變更為：

public class TestApp {

public static void main(String[] args) throws Exception {
SqlSession sqlSession = SqlSessionUtil.getSqlSession();
//GoodsModel goodsModel = new GoodsModel();
Goods goods = new Goods();
goods.setId(1);
goods.setName("c");
goods.setDescription("c");
goods.setPrice(2d);
//goodsModel.setPrice2(5d);
List<Goods> list = sqlSession.selectList("Goods.selByCondition4if", goods);
System.out.println(list);
sqlSession.close();
}
}

最後控制檯輸出為

There is no getter for property named 'price2' in 'class com.test.pojo.Goods'