在JSON对象中强制执行非空字段

Question

我们的REST API接收一些JSON对象输入,其中某些字段必须不为null.那些可以是String/Integer,也可以是其他类实例作为引用.

我们试图找到一种方法来强制这些字段不为空,而不是在api中进行空检查的正确方法.当前:

if (myObject.getSomeOtherObject() == null)
    throw new SomeException();

我们想拥有的是:

class MyObject{
    @Required
    OtherObject someOtherObject;
    // ...
}

我们尝试了3件事:

• 升级到jackson 2.0.6并使用注释com.fasterxml.jackson.annotation.JsonProperty但是,这看起来不起作用.找到了这些参考文献:http: //jira.codehaus.org/browse/JACKSON-767

• 扩展JsonDeserializer以检查null但问题是它甚至没有在null输入上执行.

public class NotNullDeserializer<T> extends JsonDeserializer<T> {

    @Override
    public T deserialize(JsonParser jsonparser, DeserializationContext deserializationcontext) throws IOException, JsonProcessingException {

        ParameterizedType superClass = (ParameterizedType) getClass().getGenericSuperclass();
        Class<T> type = (Class<T>) superClass.getActualTypeArguments()[0];

        T t = jsonparser.readValueAs(type);

        if (t == null){
            String classNameField = type.getName();
            String field = jsonparser.getCurrentName();
            throw new WrongInputException("The field '"+field+"' of type '"+classNameField+"' should not be null.");
        }

        return t;
    }
}

public class NotNullAddressDeserializer extends NotNullDeserializer<Address> {

}

@JsonDeserialize(using=NotNullAddressDeserializer.class)
    Address to;

• 编写我们自己的@Required注释并尝试使用ResourceFilter进行检查,但似乎我无法从ContainerRequest获取实际对象,即使我们可以,也不确定如何在object.otherObject.someObject.fieldNotNullable中执行对空引用的深度检查

private class Filter implements ResourceFilter, ContainerRequestFilter {
    private final ArrayList<String> requiredParameters;

    protected Filter() {
        requiredParameters = null;
    }

    protected Filter(ArrayList<String> requiredParameters) {
        this.requiredParameters = requiredParameters;
    }

    @Override
    public ContainerRequestFilter getRequestFilter() {
        return this;
    }

    @Override
    public ContainerResponseFilter getResponseFilter() {
        return null;
    }


    @Override
    public ContainerRequest filter(ContainerRequest request) {
        if (requiredParameters != null && requiredParameters.size() > 0) {
            MultivaluedMap<String, String> params = request.getQueryParameters();
            params.putAll(request.getFormParameters());
            StringBuffer missingParams = new StringBuffer();
            for (String reqParam : requiredParameters) {
                List<String> paramValues = params.get(reqParam);
                if (paramValues == null || paramValues != null && paramValues.size() == 0)
                    missingParams.append(reqParam + ",");
            }
            if (missingParams.length() > 0)
                throw new WrongInputException("Required parameters are missing: " + missingParams);
        }
        return request;
    }
}

任何帮助和见解表示赞赏.

Answer 1

JAX-RS很好地将反序列化与验证分开,即杰克逊在设计时没有任何机制来强制执行值non-null等等.相反,您可以使用BeanValidation:

1. javax.validation:validation-api在provided范围内添加依赖项.
2. 将javax.validation.constraints.NotNull注释添加到您的字段.

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