Java 新手如何使用Spring MVC 中的查询字符串和查询参数

目录

前言 

 什么是查询字符串和查询参数？

Spring MVC中的查询参数 

处理可选参数

处理多个值

处理查询参数的默认值

处理查询字符串

示例：创建一个RESTful服务 

总结

---

前言 

 什么是查询字符串和查询参数？

https://example.com/products?category=electronics&price=100

Spring MVC中的查询参数 

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

@Controller
public class ProductController {

    @RequestMapping("/products")
    public String getProducts(
        @RequestParam String category,
        @RequestParam int price) {
        // 处理查询参数
        // ...
        return "products";
    }
}

处理可选参数

@RequestMapping("/products")
public String getProducts(
    @RequestParam String category,
    @RequestParam(required = false) Integer price) {
    // 处理查询参数
    // ...
    return "products";
}

处理多个值

@RequestMapping("/products")
public String getProducts(
    @RequestParam String category,
    @RequestParam List<String> tags) {
    // 处理多个值的查询参数
    // ...
    return "products";
}

处理查询参数的默认值

@RequestMapping("/products")
public String getProducts(
    @RequestParam(defaultValue = "all") String category,
    @RequestParam(defaultValue = "0") int price) {
    // 处理查询参数
    // ...
    return "products";
}

处理查询字符串

@RequestMapping("/products")
public String getProducts(@RequestParam Map<String, String> params) {
    // 处理查询参数的Map
    // ...
    return "products";
}

示例：创建一个RESTful服务 

public class Product {
    private String name;
    private String category;
    private double price;

    // 省略构造函数和getter/setter
}

@Controller
public class ProductController {

    private List<Product> products = new ArrayList<>();

    public ProductController() {
        // 初始化产品列表
        products.add(new Product("Laptop", "Electronics", 799.99));
        products.add(new Product("Headphones", "Electronics", 149.99));
        products.add(new Product("T-shirt", "Clothing", 19.99));
    }

    @RequestMapping("/products")
    public ResponseEntity<List<Product>> getProducts(
        @RequestParam(required = false) String category,
        @RequestParam(defaultValue = "0") double maxPrice) {
        List<Product> result = new ArrayList<>();

        for (Product product : products) {
            if ((category == null || product.getCategory().equals(category)) &&
                product.getPrice() <= maxPrice) {
                result.add(product);
            }
        }

        return new ResponseEntity<>(result, HttpStatus.OK);
    }
}

总结