SpringMVC之matrixVariable

matrixVariable允许我们非常方便地进行多条件组合查询！这里我以商品查询为例，详细介绍matrixVariable的使用。
我们经常有如下需求：查询一定价格区间的商品；查询某些类别的商品；查询某些生产者的商品……第一反应你是不是想到了使用pojo封装查询条件，然后快速完成查询功能？抱歉，这里你看不到我用pojo的实现。但你可以试着看看使用SpringMVC的matrixVariable是怎么实现的。
先看看查询的展示结果：
1.没有使用查询条件查询结果：

2.使用查询条件查询一(类别，价格区间，生产者)：

3.使用查询条件查询二(品牌，类别)：

下面分个讲解条件查询……
按照类别，价格区间，生产者查询，其实最后一个查询条件使用@RequestParam，类别使用@PathVariable，真正使用到matrixVariable的是 价格区间。

Controller层代码：

@RequestMapping("/{category}/{ByCriteria}")
    public String filterProducts(
            @PathVariable("category") String category,
            @MatrixVariable(pathVar="ByCriteria") Map<String, List<String>> filterParams,
            @RequestParam("manufacturer") String manufacturer, Model model) {

        model.addAttribute("products", productService.getProductsByCriteria(category, filterParams, manufacturer));
        return "products";
    }

Service层代码：

public Set<Product> getProductsByCriteria(String category, Map<String, List<String>> filterParams, String manufacturer) {
        return productRepository.getProductsByCriteria(category, filterParams, manufacturer);
    }

Dao层代码：

public Set getProductsByCriteria(String category, Map<String, List<String>> filterParams, String manufacturer) {

        Set productsByPrice = new HashSet();
        Set productsByManufacturer = new HashSet();

        Set productsByCategory = new HashSet(getProductByCategory(category));

        Set<String> criterias = filterParams.keySet();

        if(criterias.contains("low")) {
            for(String lowPrice : filterParams.get("low")) {
                productsByPrice = getByPrice(lowPrice, ">");
            }
        }
        if(criterias.contains("high")) {
            for(String highPrice : filterParams.get("high")) {
                productsByPrice.retainAll(getByPrice(highPrice, "<"));
            }
        }
        productsByManufacturer = new HashSet(getProductsByManufacturer(manufacturer));

        productsByCategory.retainAll(productsByPrice);
        productsByPrice.retainAll(productsByManufacturer);

        return productsByCategory;
    }

public List getProductByCategory(String category) {

        List productsByCategory = new ArrayList();

        for(Product product : listOfProducts) {
            if(category.equalsIgnoreCase(product.getCategory())) {
                productsByCategory.add(product);
            }
        }
        return productsByCategory;
    }

private Set<Product> getByPrice(String price, String signal) {

        Set<Product> productByPrice = new HashSet<Product>();
        BigDecimal decimalPrice = new BigDecimal(price);

        if(signal.equals("<")) {
            for(Product product : listOfProducts) {
                if(product.getUnitPrice().compareTo(decimalPrice)<0) {
                    productByPrice.add(product);
                }
            }
        }
        else if(signal.equals(">")) {
            for(Product product : listOfProducts) {
                if(product.getUnitPrice().compareTo(decimalPrice)>0) {
                    productByPrice.add(product);
                }
            }
        }

        return productByPrice;
    }

public List getProductsByManufacturer(String manufacturer) {

        List productsByManufactures = new ArrayList();

        for(Product product : listOfProducts) {
            if(manufacturer.equalsIgnoreCase(product.getManufacturer())) {
                productsByManufactures.add(product);
            }
        }
        return productsByManufactures;
    }

SpringMVC配置文件中配置如下：

<mvc:annotation-driven enable-matrix-variables="true"/>

一切OK!
根据 品牌，类别查询代码如下：

@RequestMapping("/filter/{ByCriteria}")
    public String getProductsByFilter(@MatrixVariable(pathVar="ByCriteria")
            Map<String, List<String>> filterParams, Model model) {

        model.addAttribute("products", productService.getProductsByFilter(filterParams));
        return "products";
    }

public Set<Product> getProductsByFilter(Map<String, List<String>> filterParams) {
        return productRepository.getProductsByFilter(filterParams);
    }

public Set getProductsByFilter(Map<String, List<String>> filterParams) {

        Set productsByBrand = new HashSet();
        Set productsByCategory = new HashSet();

        Set<String> criterias = filterParams.keySet();

        if(criterias.contains("brand")) {
            for(String brandName : filterParams.get("brand")) {
                for(Product product : listOfProducts) {
                    if(brandName.equalsIgnoreCase(product.getManufacturer())) {
                        productsByBrand.add(product);
                    }
                }
            }
        }
        if(criterias.contains("category")) {
            for(String category : filterParams.get("category")) {
                productsByCategory.addAll(this.getProductByCategory(category));
            }
        }

        productsByCategory.retainAll(productsByBrand);

        return productsByCategory;
    }

完成！