将类从2更改为1时的Spring POST 400 Bad Request Postman [英] Spring POST 400 Bad Request Postman when changing class from 2 to 1 parameter
问题描述
我的@RestController类中包含以下代码:
I have following code in my @RestController class:
@RequestMapping("api/")
@RestController
public class RecommendationsController {
@PostMapping(path = "cart")
public List<RecommendationDTO> getCartRecommendations(@NonNull @RequestBody List<CartItemDTO> cart){
System.out.println(cart);
return null;
}
}
这是我的CartItemDTO类中的代码:
This is the code in my CartItemDTO class:
public class CartItemDTO {
private String productId;
private Double quantity;
public CartItemDTO(String productId, Double quantity) {
this.productId = productId;
this.quantity = quantity;
}
public String getProductId() {
return productId;
}
public Double getQuantity(){
return quantity;
}
这是我与邮递员发送的请求:
And this is the request that I send with postman:
[
{
"productId": "20000010",
"quantity": 5.0;
},
{
"productId": "20000011",
"quantity": 7.0;
}
]
这是可行的,但是当我更改代码时,如下所示,我收到错误的请求:
错误的语法
This is working but when I change my code like following, I get Bad Request: bad syntax
public class CartItemDTO {
private String productId;
public CartItemDTO(String productId) {
this.productId = productId;
}
public String getProductId() {
return productId;
}
}
有请求:
[
{
"productId": "20000010"
},
{
"productId": "20000011"
}
]
有人知道可能是什么
推荐答案
主要问题是Jackson无法构造DTO实例。
两种方法解决此问题:
1.指定默认构造函数:
-指定参数化构造函数时,Java编译器将不会添加默认构造函数。
The main issue is Jackson unable to construct instance of a DTO.
Two ways to solve this issue:
1. Specify the default constructor:
- when you specify parameterized constructor, then the Java compiler will not add default constructor.
现在您的第一个请求:
curl --location --request POST 'localhost:8080/cart' \
--header 'Content-Type: application/json' \
--data-raw '[
{
"productId": "20000010",
"quantity": 5.0
},
{
"productId": "20000011",
"quantity": 7.0
}
]'
抛出错误:
"timestamp": "2020-04-27T12:08:28.497+0000",
"status": 500,
"error": "Internal Server Error",
"message": "Type definition error: [simple type, class hello.dto.CartItemDTO]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `hello.dto.CartItemDTO` (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator)\n at [Source: (PushbackInputStream); line: 3, column: 9] (through reference chain: java.util.ArrayList[0])",
"path": "/cart"
将默认构造函数添加到DTO时,一切都按预期工作。
on adding default constructor to DTO, everything works fine as expected.
public class CartItemDTO {
private String productId;
private Double quantity;
public CartItemDTO() {
}
public CartItemDTO(String productId, Double quantity) {
this.productId = productId;
this.quantity = quantity;
}
public String getProductId() {
return productId;
}
public Double getQuantity() {
return quantity;
}
}
由于OP没有 RecommendationDTO
对象,仅将System.out.println添加为输出:
Since OP does not have RecommendationDTO
object, adding just System.out.println as output:
[hello.dto.CartItemDTO@145e35d6, hello.dto.CartItemDTO@25df553f]
- 仅DTO中的ProductId
public class CartItemDTO {
private String productId;
public CartItemDTO() {
}
public CartItemDTO(String productId, Double quantity) {
this.productId = productId;
}
public String getProductId() {
return productId;
}
}
请求:
curl --location --request POST 'localhost:8080/cart' \
--header 'Content-Type: application/json' \
--data-raw '[
{
"productId": "20000010"
},
{
"productId": "20000011"
}
]'
输出:
[hello.dto.CartItemDTO@42ad1f23, hello.dto.CartItemDTO@777d8eb3]
- 解决方案二:需要指示Jackson使用以下命令创建dto对象具有以下实例字段的构造函数:
将DTO更改为
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
public class CartItemDTO {
private String productId;
private Double quantity;
@JsonCreator
public CartItemDTO(@JsonProperty(value = "productId", required = true) String productId,
@JsonProperty(value = "quantity", required = true) Double quantity) {
this.productId = productId;
this.quantity = quantity;
}
public String getProductId() {
return productId;
}
public Double getQuantity() {
return quantity;
}
}
或仅具有productId的
OR with only productId
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
public class CartItemDTO {
private String productId;
@JsonCreator
public CartItemDTO(@JsonProperty(value = "productId", required = true) String productId) {
this.productId = productId;
}
public String getProductId() {
return productId;
}
}
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