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

Question

application.properties中的以下设置是什么？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。 always和 never值是不言自明的，但我不明白 on-param .

Answer 1

首先，我所做的是在 server.error.include-binding-errors 上进行全局搜索。在图书馆里，这让我找到了 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在这里，值类是 IncludeAttribute .通过查看 IncludeAttribute#ON_PARAM 中的文档

public static final ErrorProperties.IncludeAttribute ON_PARAM
Add error attribute when the appropriate request parameter is not "false".

我们知道 errors当请求参数不是“false”时，将添加属性。

如果你想要一些具体的东西，让我们考虑下面的例子:
Controller

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当我们使用参数 运行时错误=假

curl -H "Content-Type: application/json" --data '{"canBeNull":""}' -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"
} 

当我们使用参数 运行时错误=真

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

结果将包括 errors作为

{
    "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"
}

引用:
Web 响应式的实现
DefaultErrorWebExceptionHandler#isIncludeBindingErrors
AbstractErrorWebExceptionHandler#isBindingErrorsEnabled
Web servlet 的实现
BaseErrorController#isIncludeBindingErrors
AbstractErrorController#isBindingErrorsEnabled