杰克逊反序列化错误处理

小编典典

杰克逊反序列化错误处理

json

我的问题很简单：我有以下简单的类：

public class Foo {
   private int id = -1;
   public void setId(int _id){ this.id = _id; }
   public int getId(){ return this.id; }
}

我正在尝试处理以下JSON：

{
  "id": "blah"
}

显然，这里存在一个问题（“ blah”无法解析为int）

以前，Jackson抛出类似org.codehaus.jackson.map.JsonMappingException的内容：无法从字符串值’blah’构造java.lang.Integer的实例：不是有效的Integer值

我同意这一点，但是我想在某个地方注册一些东西，以忽略这种类型的映射错误。我尝试使用注册的DeserializationProblemHandler进行尝试（请参阅此处），但它似乎仅适用于未知属性，而不适用于反序列化问题。

您对此问题有任何线索吗？

阅读 202

2020-07-27

共1个答案

小编典典

感谢Jackson
Jackson的Tatu，我成功解决了我的问题。

对于在Jackson中处理的每个原始类型，我必须使用自定义非阻塞解串器。像这样的工厂：

public class JacksonNonBlockingObjectMapperFactory {

    /**
     * Deserializer that won't block if value parsing doesn't match with target type
     * @param <T> Handled type
     */
    private static class NonBlockingDeserializer<T> extends JsonDeserializer<T> {
        private StdDeserializer<T> delegate;

        public NonBlockingDeserializer(StdDeserializer<T> _delegate){
            this.delegate = _delegate;
        }

        @Override
        public T deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
            try {
                return delegate.deserialize(jp, ctxt);
            }catch (JsonMappingException e){
                // If a JSON Mapping occurs, simply returning null instead of blocking things
                return null;
            }
        }
    }

    private List<StdDeserializer> jsonDeserializers = new ArrayList<StdDeserializer>();

    public ObjectMapper createObjectMapper(){
        ObjectMapper objectMapper = new ObjectMapper();

        SimpleModule customJacksonModule = new SimpleModule("customJacksonModule", new Version(1, 0, 0, null));
        for(StdDeserializer jsonDeserializer : jsonDeserializers){
            // Wrapping given deserializers with NonBlockingDeserializer
            customJacksonModule.addDeserializer(jsonDeserializer.getValueClass(), new NonBlockingDeserializer(jsonDeserializer));
        }

        objectMapper.registerModule(customJacksonModule);
        return objectMapper;
    }

    public JacksonNonBlockingObjectMapperFactory setJsonDeserializers(List<StdDeserializer> _jsonDeserializers){
        this.jsonDeserializers = _jsonDeserializers;
        return this;
    }
}

然后以这种方式调用它（仅将要成为非阻塞对象的那些作为反序列化器传递）：

JacksonNonBlockingObjectMapperFactory factory = new JacksonNonBlockingObjectMapperFactory();
factory.setJsonDeserializers(Arrays.asList(new StdDeserializer[]{
    // StdDeserializer, here, comes from Jackson (org.codehaus.jackson.map.deser.StdDeserializer)
    new StdDeserializer.ShortDeserializer(Short.class, null),
    new StdDeserializer.IntegerDeserializer(Integer.class, null),
    new StdDeserializer.CharacterDeserializer(Character.class, null),
    new StdDeserializer.LongDeserializer(Long.class, null),
    new StdDeserializer.FloatDeserializer(Float.class, null),
    new StdDeserializer.DoubleDeserializer(Double.class, null),
    new StdDeserializer.NumberDeserializer(),
    new StdDeserializer.BigDecimalDeserializer(),
    new StdDeserializer.BigIntegerDeserializer(),
    new StdDeserializer.CalendarDeserializer()
}));
ObjectMapper om = factory.createObjectMapper();

2020-07-27