在框架中，筛选描述类有两种（FilterDescriptor, FilterGroupDescriptor），这里我们主要举例来说明FilterDescriptor用法。
FilterDescriptor 定义可以参照：FilterDescriptor类
准备工作
创建一张产品表
CREATE TABLE product (
product_id INT PRIMARY KEY,
category_id INT NOT NULL,
product_name VARCHAR (50) NOT NULL,
price DECIMAL
);添加测试数据
INSERT INTO product (product_id, category_id, product_name, price) VALUES
(1, 1, 'Northwind Traders Chai', 18.0000),
(2, 2, 'Northwind Traders Syrup', 7.5000),
(3, 2, 'Northwind Traders Cajun Seasoning', 16.5000),
(4, 3, 'Northwind Traders Olive Oil', 16.5000);添加Entity，Entity定义参照： 基本概念
// 类名和表名做了映射
@Table(name = "product")
public class Product {
// 这里的productID 属性做了和数据库列的映射
@Column(name = "product_id")
private Integer productID;
private String productName;
private BigDecimal price;
private Integer categoryID;
// get/set ...
}添加Mapper
@Mapper
public interface NorthwindDao {
List<Product> getProductByDynamic(Map<String, Object> params);
}添加到xml
<select id="getProductByDynamic" parameterType="java.util.Map"
resultType="com.github.wz2cool.dynamic.mybatis.db.model.entity.table.Product">
SELECT * FROM product
<if test="whereExpression != null and whereExpression != ''">WHERE ${whereExpression}</if>
<if test="orderExpression != null and orderExpression != ''">ORDER BY ${orderExpression}</if>
</select>开始筛选
简单id 筛选
@Test
public void simpleDemo() throws Exception {
FilterDescriptor idFilter =
new FilterDescriptor(FilterCondition.AND,
"productID", FilterOperator.GREATER_THAN_OR_EQUAL, 2);
Map<String, Object> queryParams =
mybatisQueryProvider.getWhereQueryParamMap(
roduct.class, "whereExpression", idFilter);
northwindDao.getProductByDynamic(queryParams);
}结果输出，这里其实已经可以看到了动态查询拼接的sql其实是站位符（防止sql注入）。
==> Preparing: SELECT * FROM product WHERE (product_id >= ?)
==> Parameters: 2(String)
<== Columns: PRODUCT_ID, CATEGORY_ID, PRODUCT_NAME, PRICE
<== Row: 2, 2, Northwind Traders Syrup, 7.5000
<== Row: 3, 2, Northwind Traders Cajun Seasoning, 16.5000
<== Row: 4, 3, Northwind Traders Olive Oil, 16.5000
<== Total: 3多筛选
@Test
public void multiFilterDemo() throws Exception {
FilterDescriptor idFilter =
new FilterDescriptor(FilterCondition.AND,
"productID", FilterOperator.GREATER_THAN_OR_EQUAL, 2);
FilterDescriptor priceFilter =
new FilterDescriptor(FilterCondition.AND,
"price", FilterOperator.LESS_THAN, 15);
Map<String, Object> queryParams =
mybatisQueryProvider.getWhereQueryParamMap(
Product.class, "whereExpression", idFilter, priceFilter);
Product productView =
northwindDao.getProductByDynamic(queryParams).stream().findFirst().orElse(null);
assertEquals(Integer.valueOf(2), productView.getProductID());
}很容易多加了一个priceFilter, 结果输出如下：
==> Preparing: SELECT * FROM product WHERE (product_id >= ? AND price < ?)
==> Parameters: 2(String), 15(String)
<== Columns: PRODUCT_ID, CATEGORY_ID, PRODUCT_NAME, PRICE
<== Row: 2, 2, Northwind Traders Syrup, 7.5000
<== Total: 1结束
用最简单两个例子大概入了一个门，是不是很简单？能想到的有几个应用场景：
- Filter 是最后动态加上去的，所以你可以在你的代码中任意地方根据你的条件生成Filter。
- 可以剥离生成Filter以达到Filter复用性。
关注我
最后大家可以关注我和 Mybatis-Dynamic-query项目 ^_^
Follow @wz2cool Star Fork