I have a bean with an arbitrary JsonValue property which I need to marshal/unmarshal from JSON.
public class MyBean {
public String name;
public JsonValue data;
}
Since JsonValue is the standard javax.json.JsonValue, I was expecting MOXy to marshal/unmarshal it out of the box, instead I got a plain string:
{
"name": "foo",
"data": "{\"some\":\"json\"}"
}
where I was expecting this:
{
"name": "foo",
"data": {
"some": "json"
}
}
When unmarshalling, data becomes null. How can I use JsonValues and get MOXy manage them like expected?
(I need to stick with default Jersey/MOXy, so no use of other libraries.)
Note: this is not an answer (solution for the OP). I typed it out before I read "I need to stick with default Jersey/MOXy". Was going to change to a comment, but there's too much stuff. I'll just leave it up for future readers.
There is a different provider for the javax.json classes. MOXy doesn't know how to handle them the way you expect. Without looking at any source code I would guess that what you are seeing is the value of toString() from the JsonValue instance. This is what will happen if the type can't be handled. You'll just get a toString() call.
Even if you add the dependency I linked to, you still have the problem that different providers don't interact with each other. What would need to happen is that in the middle of MOXy serializing the MyBean instance, if it sees a javax.json object, it tries to look for a different provider to handle it. It just doesn't work like that. Only one provider will be used.
The only solution I can think of is to instead of using MOXy, use Jackson, which has a module that supports javax.json. If you register that module with Jackson, it will know how to handle the javax.json types, "mid-serialization". You can have a look at this answer, which describes the step you should take to make it work with Jackson.
Related
I have some code that pulls data from a DB and populates a POJO. That POJO then gets serialized and pushed into an elasticsearch cluster.
The problem I am having is that one of the fields in the database was free text and people just put in a to get around the required field.
I'd like to be able to strip that whitespace out when pushing to elastic.
Here's an example of my pojo
public class Destination {
Long id;
...
...
String Address;
}
I am using Jackson to turn this into JSON using the ObjectMapper class. ie
mapper.convertTo(dest, Map.class)
When I view the value in elastic I am seeing:
{"id":1, ..., "address": " "}
Ideally, in this case, I'd just like to see the "id" property since the "address" is essentially null.
I've tried using ObjectMapper's serialization properties, but nothing seems to be working. Is there a standard way that this is being handled? How does Spring handle this?
I've seen similar questions asked (Jackson Json Serialization : Remove Blank strings), but I'm not sure how to apply that solution globally, rather than just at the class level, or if you can apply it globally.
I am receiving massive json objects from a service and so far i've been creating POJOs to match the json that comes in.
However, this is getting far too tedious as with every different service I hit I have to build 15-20 new model classes to represent the new service i'm hitting.
In short, what i'm looking for is a way to get a value I need from a neested object in the json as below (sorry for format):
random1 {
random2 {
arrayOfRandoms
}
random3 {
random4 {
random5 {
someValueIWant
}
}
}
}
so in this case I want random5s someValueIWant object. I want to get it without creating the models for random1/3/4/5 as i've been doing this whole time.
I should mention that I use Jacksons ObjectMapper to turn the json into java objects.
Hope this makes sense.
You could experiment with this online pojo generator:
http://www.jsonschema2pojo.org/
It will generate java classes from plain json (or json schema) and even add jackson annotations.
Make sure you check "Allow additional properties".
It requires valid json as input, so don't forget double quotes around fields names and values
If you find yourself doing that often, there's even scriptable versions and maven plugins.
Let's say we have following JSON,
{
"id": "imgsId1",
"type": "Fruits",
"name": "Tropical",
"image":
{
"url": "images/img1.jpg",
"width": 300,
"height": 300
},
"thumbnail":
{
"url": "images/thumbnails/img11.jpg",
"width": 50,
"height": 50
}
}
And in Java Class, we have all fields matching with above JSON.
Each time list of fields to be Deserialized depends on customer who sends the information.
For example for customer 1, we want to only read back following values, (and skip other properties even if provided in JSON)
String[] propertiesToFilter1 = {"type","image.url"};
For example for customer 2, we want to read back following values, (and skip other properties even if provided in JSON)
String[] propertiesToFilter2 = {"type","image.url", "image.width"};
When Deserializing JSON using Jackson, is it possible to provide above array which includes which fields need to be Deserialized,
ImageInfo obj1 = (ImageInfo)objectMapper.readValue(jsonStr, ImageInfo.class);
Update:
On researching on net, i saw that one of the options could be via using
FilterProvider filterProvider = new SimpleFilterProvider().addFilter("filterName1",
SimpleBeanPropertyFilter.serializeAllExcept(propertiesToFilter1));
objectMapper.setFilters(filterProvider);
But i think this is good, if we want to keep reusing the same "filterName1" for multiple customers.
In this scenario, it's little bit different because, we customize list of fields each customer can update. So each customer has different list of JSON fields they can update in different classes.
If we start defining different filter names for each customer, it will be a long list, and lookup will have performance impact.
So was looking for solution, where i can check list of fields allowed to be processed at runtime, when constructing back object using objectMapper.readValue() method.
Update 2 (Apr 25 2016):
Going through other Jackson questions, saw a similar question here,
Jackson Dynamic filtering of properties during deserialization
Using the approach listed below by creating custom "static ObjectMapper", the issue with this approach is we running Reflection API multiple times.
First time Jackson parser is populating all fields using
Reflection API when Deserializing JSON to Java Object
Second time, since we can't take all fields that were populated by
Jackson parser, for populate data into another object, we again need to run through Reflection API to populate another object.
This could result in lot of overhead.
Using the approach defined in above link provided, i think using "BeanDeserializerModifier" seems to be best approach. Now the question is, since we are also using Factory based approach to initialize ObjectMapper, we don't want to hard code all arrays for different customers.
Wanted to check if it's possible to provide the String[] array with list of Properties to be considered at runtime to "BeanDeserializerModifier"?
something similar to,
String[] propertiesToFilter2 = {"type","image.url", "image.width"};
BeanDeserializerModifier curBeanDeserializerModifier =
getBeanDeserializerModifierInstance();
curBeanDeserializerModifier.setPropertiesToConsider(propertiesToFilter2);
Thanks
use #JsonIgnoreProperties with configure parameters
http://www.programcreek.com/java-api-examples/index.php?api=com.fasterxml.jackson.annotation.JsonIgnoreProperties
I am not sure if there is a possibility to configure the deserialization dynamically with annotations.
I would suggest to create a class with a static ObjectMapper. In this class you can create different implementations of deserialization. The business logic of your application should then decide which implementation should be used for which customer. Inside your different implementations you are able to configure the ObjectMapper like you do it with annotations.
A second solution can be to deserialize the full json for every customer and let the business logic decide which fields/objects of the Pojo is used. This needs also an implementation in your application.
The benefit of the implementation of the configuration in the business logic is that you will have cleaner code and one place where your configuration is done for every customer.
static ObjectMapper information
I have a RESTful web service that provides JSON that I am consuming. I am using Spring 3.2 and Spring's MappingJacksonHttpMessageConverter. My JSON looks like this:
{
"Daives": {
"Daive": {},
"Daive": {},
"Daive": {},
"Daive": {}
}
}
Now everything I have read seems to indicate that this JSON should be refactored to an array of JSON Daives. However, this is valid JSON so I want to make sure that I am thinking correctly before going back to the service provider to ask for changes. In the format above, I would have to know ahead of time how many Daives there are going to be such that my DTO accounted for them. The handy dandy Jackson mapper isn't going work with this kind of JSON setup. If the JSON was altered to provide and Array of JSON Daives, I could use a List to dynamically map them using Spring/Jackson.
Am I correct? Thanks :)
According to this thread, the JSON spec itself does not forbid multiple fields with the same name (in your case, multiple fields named "Daive" in the object "Daives").
However, most parsers will either return an error or ignore any value but the last one. As you said, putting these values into an array seems much more sensible; and indeed, you'll be able to map this array to a List with Jackson.
I am currently working on a vertx.io application and wanted to use the provide mongo api for data storage. I currently have a rather clunky abstraction on top of the stock JsonObject classes where all get and set methods are replaced with things like:
this.backingObject.get(KEY_FOR_THIS_PROPERTY);
This is all well and good for now, but it won't scale particularly well. it also seems dirty, specifically when using nested arrays or objects. For example, if I want to be able to fill fields only when actual data is known, I have to check if the array exists, and if it doesn't create it and store it in the object. Then I can add an element to the list. For example:
if (this.backingObject.getJsonArray(KEY_LIST) == null) {
this.backingObject.put(KEY_LIST, new JsonArray());
}
this.backingObject.getJsonArray(KEY_LIST).add(p.getBackingObject());
I have thought about potential solutions but don't particularly like any of them. Namely, I could use Gson or some similar library with annotation support to handle loading the object for the purposes of manipulating the data in my code, and then using the serialize and unserialize function of both Gson and Vertx to convert between the formats (vertx to load data -> json string -> gson to parse json into pojos -> make changes -> serialize to json string -> parse with vertx and save) but that's a really gross and inefficient workflow. I could also probably come up with some sort of abstract wrapper that extends/implements the vertx json library but passes all the functionality through to gson, but that also seems like a lot of work.
Is there any good way to achieve more friendly and maintainable serialization using vertx?
I just submitted a patch to Vert.x that defines two new convenience functions for converting between JsonObject and Java object instances without the inefficiency of going through an intermediate JSON string representation. This will be in version 3.4.
// Create a JsonObject from the fields of a Java object.
// Faster than calling `new JsonObject(Json.encode(obj))`.
public static JsonObject mapFrom(Object obj)
// Instantiate a Java object from a JsonObject.
// Faster than calling `Json.decodeValue(Json.encode(jsonObject), type)`.
public <T> T mapTo(Class<T> type)
Internally this uses ObjectMapper#convertValue(...), see Tim Putnam's answer for caveats of this approach. The code is here.
I believe Jackson's ObjectMapper.convertValue(..) functions don't convert via String, and Vert.x is using Jackson for managing JsonObject anyway.
JsonObject just has an underlying map representing the values, accessible via JsonObject.getMap(), and a Jackson serializer/deserializer on the public ObjectMapper instance in io.vertx.core.json.Json.
To switch between JsonObject and a data model expressed in Pojos serializable with Jackson, you can do:
JsonObject myVertxMsg = ...
MyPojo pojo = Json.mapper.convertValue ( myVertxMsg.getMap(), MyPojo.class );
I would guess this is more efficient than going via a String (but its just a guess), and I hate the idea of altering the data class just to suit the environment, so it depends on the context - form vs performance.
To convert from Pojo to JsonObject, convert to a map with Jackson and then use the constructor on JsonObject:
JsonObject myobj = new JsonObject ( Json.mapper.convertValue ( pojo, Map.class ));
If you have implied nested JsonObjects or JsonArray objects in your definition, they will get instantiated as Maps and Lists by default. JsonObject will internally re-wrap these when you access fields specifying those types (e.g. with getJsonArray(..).
Because JsonObject is freeform and you're converting to a static type, you may get some unwanted UnrecognizedPropertyException to deal with. It may be useful to create your own ObjectMapper, add the vertx JsonObjectSerializer and JsonArraySerializer, and then make configuration changes to suit (such as DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES in Jackson).
Not sure if I've understood you correctly, but it sounds like you're trying to find a simple way of converting POJOs to JsonObject?
So, we have lots of pojos that we send over the EventBus as JsonObjects
I've found the easiest way is to use the vert.x Json class which has loads of helper methods to convert to / from Json Strings
JsonObject jsonObject = new JsonObject(Json.encode(myPojo));
Sometimes you need to add some custom (de)serializers, but we always stick with Jackson - that is what Vert.x is using so they work out of the box.
What we actually do, is provide an interface like the following:
public JsonObjectSerializable {
public JsonObject toJson();
}
And all our pojos that need to be sent over the EventBus have to implement this interface.
Then our EventBus sending code looks something like (simplified):
public <T extends JsonObjectSerializable> Response<T> dispatch(T eventPayload);
Also, as we generally don't unit test Pojos, adding this interface encourages the developers to unit test their conversion.
Hope this helps,
Will
Try this:
io.vertx.core.json.Json.mapper.convertValue(json.getMap(), cls)
I think that using Gson as you described is the best possible solution at the current time.
While I agree that if a protocol layer was included in Vert.x it would indeed be first prize, using Gson keeps your server internals pretty organised and is unlikely to be the performance bottleneck.
When and only when this strategy becomes the performance bottleneck have you reached the point to engineer a better solution. Anything before that is premature optimisation.
My two cents.
You can try:
new JsonObject().mapFrom(object)