I am able to load some entities into ElasticSearch with out-of-the box Spring Data ElasticSearch. The thing is my model classes contemplate many properties and for some of those I don't want my representation (typing) be reflected into ES.
#Field(serializer = MyCustomSerializer, deserializer = MyCustomDeserializer)
private SomeClass someObject;
I'd like, for example, for SomeClass to be serialized as a String, so I can query it as such. Also, when reading data from ES, I want to be able to write a custom deserializer (MyCustomDeserializer) to convert this String into my own model.
Is there any way I can accomplish that??
Thanks
Spring Data ElasticSearch uses jackson to serialize the fields, so you could achieve custom serialization logic by defining:
#JsonSerialize(using = MyCustomSerializer.class)
#JsonDeserialize(using = MyCustomDeserializer.class)
private SomeClass someObject;
Or configure your mapping globally in a jackson ObjectMapper, replacing the default EntityMapper from spring-data-elasticsearch. More on that here.
Related
I am working in a RESTful application developed in Apache CXF and I would like to introduce hypermedia functionality to it.
Most of our jaxrs:serviceBeans follow this template:
#GET
#Path("/{exampleId}")
public ExampleJSON get(#PathParam("exampleId") Integer exampleId) {
ExampleJSON example;
// Load data from repository here...
// Add link to self.
String href = javax.ws.rs.core.Link.fromResource(ExampleService.class).build().getUri().toString();
// HypermediaLink is a custom object to hold a "href" and "rel" strings
HypermediaLink linkToSelf = new HypermediaLink();
linkToSelf.setHref(href + example.getId());
linkToSelf.setRel("self");
// Inherited method, just adds a HypermediaLink to a collection in the parent class
example.addHypermediaLink(linkToSelf);
// Return JSON compatible object, JACKSON will serialize it nicely.
return example;
}
This is the basic concept. Keep in mind that I simplified this code for explanation purposes; so, it can be easily understood.
This code works fine; but I am wondering if there is a better way to do this with Apache CXF. I have some ideas for how to enhancing it; however, it will require some custom annotations.
I see some examples using Jersey, but I would like to stick with Apache CXF.
Any help would be appreciated.
Thanks
I would leverage some features of JAX-RS and / or Jackson to implement the link adding under the hood at the serialization level. So you wouldn't need to have a specific field for the link within the bean itself.
You could implement a custom MessageBodyWriter to generate a different JSON payload (for example) for your POJOs than the default. So you could dynamically add the link.
See this answer for more details: How to write an XML MessageBodyWriter provider with jersey.
If you use Jackson for the serialization, you could implement a custom serializer. Note that this is generic and will work for all supported format of Jackson.
Below is a sample code:
public class LinkBeanSerializer extends JsonSerializer<SomeBean> {
#Override
public void serialize(SomeBean bean, JsonGenerator jgen,
SerializerProvider provider) throws IOException,
JsonProcessingException {
jgen.writeStartObject();
// Fields
jgen.writeNumberField("id", bean.getId());
// Things could be generic using reflection
// Link
String href = javax.ws.rs.core.Link.fromResource(SomeBean.class).build().getUri().toString();
HypermediaLink linkToSelf = new HypermediaLink();
linkToSelf.setHref(href + bean.getId());
linkToSelf.setRel("self");
jgen.writeObjectField("hypermediaLink", linkToSelf);
jgen.writeEndObject();
}
}
Note that we could make this serializer more generic I think (something like extends JsonSerializer<Object>)
See this answer for more details: Processing JSON response using JAX-RS (how to register the custom serializer within JAX-RS, ...).
Perhaps implementing a WriterInterceptor could solve your problem but there is impact on the beans since you need to have field hypermediaLink. The interceptor could be responsible of filling the field.
See this answer for more details: Jersey Update Entity Property MessageBodyWriter.
IMO the more convenient solution is the second one. It's transparent and support all the formats supported by Jackson.
Hope it helps you,
Thierry
We are using flyweight pattern for some objects in our system. Those objects are also saved in database (mongodb). After loading the object back from db using Spring Data, there is no easy way to replace the object constructed by Spring Data with the object in the flyweight cache. For Java deserialization, there is readResolve() method. I wonder if Spring Data can add something similar to support this use case.
Is there any solutions with the current Spring Data implementation (1.4.1 release)?
They must have something otherwise enums wouldn't work either... I'd consider custom converters, e.g. here (look for the last section with PersonReadConverer):
http://docs.spring.io/spring-data/mongodb/docs/1.4.x/reference/html/mapping-chapter.html
I just hope it works when Person is a nested field inside another class - didn't get a chance to test it .
Good luck
Thanks #Pelit_Mamani for some suggestions. I did try to implement a converter and set it in mongo mapping converter and it seems to work. It works even when the object is embedded in other object.
<mongo:mapping-converter id="mappingConverter" base-package="com.mytest.domain" db-factory-ref="mongoDbFactory" disable-validation="true">
<mongo:custom-converters>
<mongo:converter>
<bean class="com.mytest.repo.converter.MyReadConverter" />
</mongo:converter>
</mongo:custom-converters>
</mongo:mapping-converter>
And the converter class:
public class MyReadConverter implements Converter<DBObject, MyObject>
I have a class defined as:
class Person {
public int age;
public String firstName;
}
Note that I use camel case for the field names. Also, I know that I could have generated getters and setters but I tend to not do that for simple domain objects.
When I deserialize a JSON or XML response in my REST API, it should spit out:
<Person><Age>11</Age><FirstName>Johnson</FirstName></Person>
You will notice that the first letter is upper-cased.
I could use, for example, #JsonPoperty("FirstName") on my POJO to get the output the way I need it, but this doesn't scale when there are too many fields. I'd like to use a custom property naming strategy (as described in How To Use Property Naming Strategy In Jackson). But instead of configuring an ObjectMapper, I was wondering if its possible to specify a naming strategy using annotations?
Thanks
In Guvnor documentation, I know how to define data enumeration and use it in Guvnor. Is it possible to fetch data enumeration from my own Java code?
From Guvnor's documentation:
Loading enums programmatically: In some cases, people may want to load their enumeration data entirely from external data source (such as a relational database). To do this, you can implement a class that returns a Map. The key of the map is a string (which is the Fact.field name as shown above), and the value is a java.util.List of Strings.
public class SampleDataSource2 {
public Map<String>, List<String> loadData() {
Map data = new HashMap();
List d = new ArrayList();
d.add("value1");
d.add("value2");
data.put("Fact.field", d);
return data;
}
}
And in the enumeration in the BRMS, you put:
=(new SampleDataSource2()).loadData()
The "=" tells it to load the data by executing your code.
Best Regards,
I hope its not too late to answer this.
To load enum from application to guvnor,
Build the enum class dynamically from string (in my case enum values is provided by user via GUI)
Add it to a jar, convert it to byte array
POST it to guvnor as asset (model jar) via REST call
Call save repository operation (change in source code of guvnor)
Now enum will be visible as fact in your rule window.
Editing/Deletion of model jar and validation of rules aftermath is something you have to take care.
I am very new to GWT.
I am using ext-gwt widgets.
I found many places in my office code containing like,
class A extends BaseModel{
private UserAccountDetailsDto userAccountDetailsDto = null;
//SETTER & GETTER IN BASEMODEL WAY
}
Also, the DTO reference is unused.
public class UserAccountDetailsDto implements Serializable{
private Long userId=null;
private String userName=null;
private String userAccount=null;
private String userPermissions=null;
//NORMAL SETTER & GETTER
}
Now, I am able to get the result from GWT Server side Code and things Work fine, but when I comment the DTO reference inside the class A, I am not getting any Result.
Please explain me the need of that.
Thanks
Well the problem is in implementation of GXT BaseModel and GWT-RPC serialization.
BaseModel is based around special GXT map, RpcMap. This map has defined special serialization rules, which let's avoid RPC type explosion, but as side effect, only some simple types stored in map will be serialized. E.g. you can put any type inside the map, but if you serialize/deserialize it, only values of type Integer, String ,Double,Byte, Float and Short (and arrays of this types) will be present. So the meaning behind putting reference to the DTO inside BaseModel, is to tell GWT-RPC that this type is also have to be serialized.
Detailed explanation
Basically GWT-RPC works like this:
When you define an interface for service, GWT-RPC analyzes all the classes used in parameters/ return type, to create serializers/deserializers. If you return something like Map<Object,Object> from your service, GWT-RPC will have to create a serializer for each class which implements Map and Serializable interfaces, but also it will generate serializers for each class which implements Serializable. In the end it is quite a bad situation, because the size of your compiled js file will be much biggger. This situation is called GWT-RPC type explosion.
So, in the BaseModel, all values are stored in RpcMap. And RpcMap has custom written serializer (RpcMap_CustomFieldSerializer you can see it's code if you interested how to create such things), so it doesn't cause the problem described above. But since it has custom serializer GWT dosn't know which custom class have been put inside RpcMap, and it doesn't generate serializers for them. So when you put some field into your BaseModel class, gwt knows that it might need to be able to serialize this class, so it will generate all the required stuff for this class.
Porting GXT2 Application code using BaseModel to GXT3 Model is uphill task. It would be more or less completely rewrite on model side with ModelProviders from GXT3 providing some flexibility. Any code that relies on Model's events, store, record etc are in for a rewrite.