java - 使用自定义 Json 输出在 DropWizard 中进行 Bean 验证

Question

我正在开发一个具有各种 Rest 功能的网络服务。我想使用标准 @Valid 注释来验证我的 bean。但是我确实想修改输出 json 错误。

验证中的错误消息当前格式如下:

{
  "errors": [
    "someString size must be between 0 and 140",
    "anotherString cannot contain numbers"
  ]
}

但是我确实希望错误消息的格式如下:

{
    "errors": [{
            "someString": "size must be between 0 and 140"
        },
        {
            "anotherString": "cannot contain numbers"
        }
    ]
}

或

{
    "errors": [{
            "field": "someString"
            "error": "size must be between 0 and 140"
        },
        {
            "field": "anotherString"
            "error": "cannot contain numbers"
        }
    ]
}

我知道如何通过向验证注释提供 message="some message about strings" 来更改错误消息，甚至使用 ValidationMEssages.properties作为所有错误消息的公共(public)位置。然而，如果发生错误，我不知道如何更改输出格式。

我已阅读以下文档，但我需要更多指导。 http://www.dropwizard.io/1.0.0/docs/manual/validation.html

这是我的第一个DropWizard项目，我习惯在Spring中开发。

提前致谢。

Answer 1

我找到了解决我自己问题的方法。如果有人遇到和我一样的问题，我决定将其发布。

这是针对 DropWizard 1.0 的，我尚未测试它是否适用于早期/更高版本，因此请记住这一点。我无法为您提供完整的解决方案，但我已经发布了我的解决方案是代码片段，因此不要指望您可以简单地复制/粘贴并编译。

解决方案实际上非常简单，您只需为 ConstraintViolationException 实现自己的 ExceptionMapper 并使用 DropWizard 重新注册即可。

您可以通过提供模板或常规文本轻松指定自己的 Bean 验证消息。 IE。

@NotNull(message="该死的，莫蒂。我要求你做一件事!")

或

@NotNull(message="{morty.error}")

模板位于 ValidationMessages.properties 中，您必须自己创建并放置在 src/main/resources/

ValidationMessages.properties

morty.error=God damn it, Morty. I ask you to do one thing!

无论如何，这是我的解决方案。

SomeApplication.class

//Class where you setup DropWizard
public class SomeApplication extends Application<SomeConfiguration> {

    @Override
    public void run(SomeConfiguration conf, Environment environment) throws Exception {

        //Remove all default ExceptionMappers
        ((DefaultServerFactory)conf.getServerFactory()).setRegisterDefaultExceptionMappers(false);

        //Register your custom ExceptionMapper for ConstraintViolationException
        environment.jersey().register(new CustomExceptionMapper());

        //Restore the default ExceptionsMappers that you just removed
        environment.jersey().register(new LoggingExceptionMapper<Throwable>() {});
        environment.jersey().register(new JsonProcessingExceptionMapper());
        environment.jersey().register(new EarlyEofExceptionMapper());
    }
}

CustomExceptionMapper.class

//This is where the magic happens. 
//This is your custom ExceptionMapper for ConstraintViolationException
@Provider
public class CustomExceptionMapper implements ExceptionMapper<ConstraintViolationException> {

    @Override
    public Response toResponse(ConstraintViolationException cve) {
        //List to store all the exceptions that you whish to output
        //ValidationErrors is a custom object, which you can see further down
        ValidationErrors validationErrors = new ValidationErrors();

        //Loop through all the ConstraintViolations
        for(ConstraintViolation<?> c : cve.getConstraintViolations()){

            //We retrieve the variable name or method name where the annotation was called from.
            //This will be your property name for your JSON output.
            String field = ((PathImpl)c.getPropertyPath()).getLeafNode().getName();

            //If field is null, then the notation is probably at a class level.
            //Set field to class name
            if(field == null){
                field = c.getLeafBean().getClass().getSimpleName();
            }

            //c.getMessage() is the error message for your annotation.
            validationErrors.add(field, c.getMessage());
        }
        //Return a response with proper http status.
        return Response.status(422).entity(validationErrors).build();
    }
}

验证错误

//There is not really any magic happening here.
//This class is just a wrapper for a List with the type ValidationObject.
public class ValidationErrors {

    public List<ValidationObject> errors = new ArrayList<ValidationObject>();

    public void add(String field, String error){
        errors.add(new ValidationObject(field, error));
    }
}

ValidationObject.class

//Once again, no magic
public class ValidationObject {

    //This will be your property names
    private String field, error;

    public ValidationObject(String field, String error){
        this.field = field;
        this.error = error;
    }

    public String getField() {
        return field;
    }

    public void setField(String field) {
        this.field = field;
    }

    public String getError() {
        return error;
    }

    public void setError(String error) {
        this.error = error;
    }
}

TestClass.class

//This is just a class to showcase the functionality
//I have not posted any codesnippers for this @CustomClassConstaint, 
//it is a custom annotaiton.
//I only included this annotation to show how  
//the CustomExceptionMapper handles annotations on a class level
@CustomClassConstaint 
public class TestClass {

    @NotNull
    @Size(min = 2, max = 5)
    public String testString1;

    @NotNull
    @Size(min = 2, max = 5)
    public String testString2;

    @Min(10)
    @Max(20)
    public int testInt1;

    @Min(10)
    @Max(20)
    public int testInt2;

}

用于测试的休息功能

    //Some rest function to showcase
    @POST
    @Path("/path/to/test")
    //Remember @Valid or annotations will not be validated
    public Response callRestTestMethod(@Valid TestClass testObject){
        return Response.ok().build();
    }

测试输入:

POST /path/to/test
{
  "testString1": null,
  "testString2": "",
  "testInt1": 9,
  "testInt2": 21
}

测试输出:

顺序有些随机，并且每次调用 callRestTestMethod(...) 时都会发生变化。验证按照组件树中的顺序一一触发，不知道是否可以控制顺序。

{
  "errors": [
    {
      "field": "TestClass",
      "error": "custom error msg"
    },
    {
      "field": "testInt1",
      "error": "must be greater than or equal to 10"
    },
    {
      "field": "testString1",
      "error": "may not be null"
    },
    {
      "field": "testInt2",
      "error": "must be less than or equal to 20"
    },
    {
      "field": "testString2",
      "error": "size must be between 2 and 5"
    }
  ]
}