Spring中的server.error.include-binding-errors=on-param有什么作用？

下面的设置是什么意思application.properties在 Spring 应用程序中做什么？

server.error.include-binding-errors=on-param

我在文档中找不到它。

The always and never价值观是不言自明的，但我不明白on-param.

首先，我所做的是进行全局搜索server.error.include-binding-errors在图书馆，这引导我到spring-configuration-metadata.json

    {
      "name": "server.error.include-binding-errors",
      "type": "org.springframework.boot.autoconfigure.web.ErrorProperties$IncludeAttribute",
      "description": "When to include \"errors\" attribute.",
      "sourceType": "org.springframework.boot.autoconfigure.web.ErrorProperties",
      "defaultValue": "never"
    },

我们看到相关的属性是errors这里，值类是IncludeAttribute。通过检查文档IncludeAttribute#ON_PARAM https://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/autoconfigure/web/ErrorProperties.IncludeAttribute.html#ON_PARAM

公共静态最终ErrorProperties.includeAttribute ON_PARAM
当适当的请求参数不为“false”时添加错误属性。

我们知道errors当请求参数不为“false”时，将添加该属性。

如果您想要具体的东西，让我们考虑以下示例：

控制器

import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import javax.validation.Valid;

@RestController
public class TestController {
    @PostMapping("/dummy")
    public String test(@Valid @RequestBody DummyDTO dummyDTO) {
        return "";
    }
}

DTO

import javax.validation.constraints.NotNull;

public class DummyDTO {
    @NotNull(message = "mandatoryText can not be null")
    private String mandatoryText;

    private String canBeNullText;

    public String getMandatoryText() {
        return mandatoryText;
    }

    public void setMandatoryText(String mandatoryText) {
        this.mandatoryText = mandatoryText;
    }

    public String getCanBeNullText() {
        return canBeNullText;
    }

    public void setCanBeNullText(String canBeNullText) {
        this.canBeNullText = canBeNullText;
    }
}

假设我们设置
server.error.include-binding-errors=on-param

当我们带参数运行时错误=假

curl -H "Content-Type: application/json" --data '{"canBeNullText":""}' -X POST http://localhost:8080/dummy?errors=false

结果将不包括errors

{
    "timestamp": "2021-06-11T13:38:29.868+00:00",
    "status": 400,
    "error": "Bad Request",
    "message": "",
    "path": "/dummy"
} 

当我们带参数运行时错误=真

curl -H "Content-Type: application/json" --data '{"canBeNullText":""}' -X POST http://localhost:8080/dummy?errors=true

结果将包括errors as

{
    "timestamp": "2021-06-11T13:51:00.649+00:00",
    "status": 400,
    "error": "Bad Request",
    "errors": [{
            "codes": ["NotNull.dummyDTO.mandatoryText", "NotNull.mandatoryText", "NotNull.java.lang.String", "NotNull"],
            "arguments": [{
                    "codes": ["dummyDTO.mandatoryText", "mandatoryText"],
                    "arguments": null,
                    "defaultMessage": "mandatoryText",
                    "code": "mandatoryText"
                }
            ],
            "defaultMessage": "mandatoryText can not be null",
            "objectName": "dummyDTO",
            "field": "mandatoryText",
            "rejectedValue": null,
            "bindingFailure": false,
            "code": "NotNull"
        }
    ],
    "path": "/dummy"
}

参考：
Web 响应式的实现
DefaultErrorWebExceptionHandler#isIncludeBindingErrors https://github.com/spring-projects/spring-boot/blob/v2.5.0/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/error/DefaultErrorWebExceptionHandler.java#L224
AbstractErrorWebExceptionHandler#isBindingErrorsEnabled https://github.com/spring-projects/spring-boot/blob/v2.5.0/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/error/AbstractErrorWebExceptionHandler.java#L214

Web servlet 的实现
BaseErrorController#isIncludeBindingErrors https://github.com/spring-projects/spring-boot/blob/v2.5.0/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/error/BasicErrorController.java#L167
AbstractErrorController#isBindingErrorsEnabled https://github.com/spring-projects/spring-boot/blob/v2.5.0/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/error/AbstractErrorController.java#L85