英文:
How to capture multiple url parameters using @RequestParam?
问题
我有这个方法：
@GetMapping("/restaurant")
public List<Restaurant> list(@RequestParam(required = false) String nameRestaurant, @RequestParam(required = false) String nameProduct){
if (nameRestaurant == null && nameProduct == null ) {
return restaurantRepository.findAll();
}
else if (!nameProduct.isEmpty()){
return restaurantRepository.findByNameProduct(nameProduct);
}
else {
return restaurantRepository.findByNameRestaurant(nameRestaurant);
}
}
只有 'IF' 和 'ELSE IF' 能正常工作并返回 JSON，而 'ELSE' 总是返回 500（NullPointerException）。如果我将 'ELSE IF' 和 'ELSE' 位置对调，原本在 'ELSE IF' 的部分将会工作，而 'ELSE' 部分则不会，是否有原因呢？
英文:
I have this method:
@GetMapping("/restaurant")
public List<Restaurant> list(@RequestParam(required = false) String nameRestaurant, @RequestParam(required = false)String nameProduct){
if (nameRestaurant== null && nameProduct== null ) {
return restaurantRepository.findAll();
}
else if (!nameProduct.isEmpty()){
return restaurantRepository.findByNameProduct(nameProduct);
}
else {
return restaurantRepository.findByNameRestaurant(nameRestaurant);
}
}
Only 'IF' and 'ELSE IF' work and return JSON, 'ELSE' always returns 500(NullPointerException). If I invert 'ELSE IF' with 'ELSE', what will be in 'ELSE IF' will work and 'ELSE' will not, is there any why?
答案1
得分: 2
我认为你在验证部分缺少了一个空值检查。第一个if语句检查nameRestaurant和nameProduct是否为null，这意味着在else或else if中，nameRestaurant或nameProduct可能为null（可能导致NullPointerException）。
可能将你的代码更改如下会起作用：
@GetMapping("/restaurant")
public List<restaurant> list(@RequestParam(required = false) String nameRestaurant,
@RequestParam(required = false) String nameProduct) {
if (nameRestaurant != null && !nameRestaurant.isEmpty()) {
return restaurantRepository.findByNameRestaurant(nameRestaurant);
}
if (nameProduct != null && !nameProduct.isEmpty()) {
return restaurantRepository.findByNameProduct(nameProduct);
}
return restaurantRepository.findAll();
}
英文:
I think you are missing a null checker in your validation. The first if checks if nameRestaurant AND nameProduct are null, meaning that during the else / else if nameRestaurant OR nameProduct might be null (possibly leading to NullPointerException).
Probably changing your code to the following would work:
@GetMapping("/restaurant")
public List<restaurant> list(@RequestParam(required = false) String nameRestaurant,
@RequestParam(required = false) String nameProduct) {
if (nameRestaurant != null && !nameRestaurant.isEmpty()) {
return restaurantRepository.findByNameRestaurant(nameRestaurant);
}
if (nameProduct != null && !nameProduct.isEmpty()) {
return restaurantRepository.findByNameProduct(nameProduct);
}
return restaurantRepository.findAll();
}
答案2
得分: 0
use urls instead:
// 获取所有餐厅
@GetMapping("/restaurant")
/restaurant
// 根据名称获取餐厅
@GET
@Path("/restaurant")
@PathParam("name")String name
/restaurant/{name}
// 根据餐厅和产品名称获取产品
@GET
@Path("/restaurant")
@PathParam("name")String name, @PathParam("product")String product
/restaurant/{name}/{product}
英文:
use urls instead:
// Get all restaurants
@GetMapping("/restaurant")
/restaurant
// Get restaurant by name
@GET
@Path("/restaurant")
@PathParam("name")String name
/restaurant/{name}
// Get product by restaurant and product name
@GET
@Path("/restaurant")
@PathParam("name")String name, @PathParam("product")String product
/restaurant/{name}/{product}
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