I am trying to display a List of items in JSON format. My code structure utilizing SpringBoot and JPA Repository on Server side:
Entity class
Repository class created
Service written (contains repository.findAll() function)
Controller class
Goal is to output the record set extracted from SQL database onto localhost:8080/api/getinspection.
I have added Gson dependency in my pom.xml and in my controller class added code to convert to JSON.
I get an error saying:
java.lang.UnsupportedOperationException: Attempted to serialize java.lang.Class: org.hibernate.proxy.HibernateProxy.
Forgot to register a type adapter?
I have researched on type adapter on stackoverflow and tried to implement the solution, but in vain. Please help.
Service class
public List<INSPCTN> getInspections() {
return inspctnRepository.findAll(); }
Controller Class
#Service
public class InspectionService {
#Autowired
INSPCTNRepository inspctnRepository;
#GetMapping(path="/getInspection", produces = "application/JSON")
public String getInspections() {
List<INSPCTN> list = inspectionService.getInspections();
Gson gson = new Gson();
String json = gson.toJson(list);
return json;
}
}
Expected result: List of records from the database in JSON format
Actual:
There was an unexpected error (type=Internal Server Error, status=500).
Attempted to serialize java.lang.Class: org.hibernate.proxy.HibernateProxy.
Forgot to register a type adapter?
Related
I'm developing a Rest Client using Spring Boot and Spring Framework (spring-boot-starter-parent 2.1.6.RELEASE)
I have a class representing a response object as shown below:
public class ValidateResponse {
private String ResponseCode;
private String ResponseDesc;
//getters and setters
//constructors using fields
//empty constructor
}
I'm creating a web-hook for an external api and I need to return a JSON object to for a specific endpoint (the JSON object properties must start with uppercase(s)). I'm calling returning the object from a PostMapping method nested in a RequestMapping root path:
#PostMapping("hooks/validate")
public ValidateResponse responseObj(#RequestHeader Map<String, String> headersObj) {
ValidateResponse response = new ValidateResponse("000000", "Success");
logger.info("Endpoint = hooks/validate | Request Headers = {}", headersObj);
return response;
}
However, when I hit the endpoint from postman I'm getting duplicate varialbes
{
"ResponseCode": "000000",
"ResponseDesc": "Success",
"responseCode": "000000",
"responseDesc": "Success"
}
I understand that the pojo-json conversion is handled by spring but I don't understand why the conversion is yielding duplicate variables.
Note: I know the ResponseDesc and the ResponseCode are not declared using the best standards for naming variables (camelCasing).
I've done some digging and according to the Java Language Specification
An identifier is an unlimited-length sequence of Java letters and Java digits, the first of which must be a Java letter.
and
The "Java letters" include uppercase and lowercase ASCII Latin letters A-Z (\u0041-\u005a), and a-z (\u0061-\u007a), and, for historical reasons, the ASCII underscore (_, or \u005f) and dollar sign ($, or \u0024). The $ character should be used only in mechanically generated source code or, rarely, to access pre-existing names on legacy systems.
So, I'm assuming its syntactically correct to define a variable using the Camelcase format [Need clarification on this].
I'm considering having to create the JSON object manually but I'd like to know the cause of this behaviour first. Any pointers are appreciated.
Jackson deserializes all the public fields that it comes across. However if you want Jackson to return the response in your expected element names (in your case elements starting with capital letters), make the fields private and annotate them with the #JsonProperty(expected_name_here). Your class file will typically looks as shown below
public class ValidateResponse {
#JsonProperty("ResponseDesc")
private String responseCode;
#JsonProperty("ResponseDesc")
private String responseDesc;
//getters and setters
//constructors using fields
//empty constructor
}
Note: The getters and setters for these fields should be public, otherwise Jackson won't see anything to deserialize in the class.
public class ValidateResponse {
#JsonProperty("ResponseDesc")
public String responseCode;
#JsonProperty("ResponseDesc")
public String responseDesc;
//getters and setters
//constructors using fields
//empty constructor
}
This must fix your problem, however I do not know the reason as it requires deep Jackson investigation.
EDIT
I found out the reason.
The field got duplicated because in you case you had:
2 public fields named in upper case -> they are to be processed by jackson
2 getters getResponseCode and getResponseDesc -> they are to be resolved
as accessors for properties responseCode and responseDesc accordingly.
Summing this up - you have 4 properties resolved by Jackson. Simply making your fields private will resolve your issue, however I still advise using JsonProperty approach.
I added a com.google.code.gson dependency in the projects pom.xml file to configure Spring Boot to use Gson (instead of the default jackson).
The Json object returned from the hooks/validate endpoint must have its property names starting with a capital letter. Using a java class to generate the response object was resulting to camelCased property names so I resolved to create the JSON response object manually. Here's the code for creating the custom JSON object:
public ResponseEntity<String> responseObj(#RequestHeader Map<String, String> headersObj) {
HttpHeaders responseHeaders = new HttpHeaders();
responseHeaders.setContentType(MediaType.APPLICATION_JSON);
JsonObject response = new JsonObject();
response.addProperty("ResponseCode", "00000000");
response.addProperty("ResponseDesc" , "Success");
logger.info("Endpoint = hooks/validate | Request Headers = {}", headersObj);
return ResponseEntity.ok().headers(responseHeaders).body(response.toString());
}
Note The JSON object is returned as a String so the response from the endpoint must have an additional header to define MediaType to inform the calling system that the response is in JSON format:
responseHeaders.setContentType(MediaType.APPLICATION_JSON);
then add the header to the response:
return ResponseEntity.ok().headers(responseHeaders).body(response.toString());
i'm trying to access the values of properties file in spring framework. now i have bean file and controller. so how to access properties file value in json formate using bean
For accessing single value can be used Spring annotations "PropertySource" and "Value".
#PropertySource("classpath:application.properties")
public class SomeClass {
#Value("${some.property}")
private String someProperty;
...
}
For accessing/looping all spring properties, check this solution looping-through-all-the-properties-in-a-file-with-spring-and-java
Controller sample code:
#RestController
public class PropertiesController {
#Autowired
Properties props;
#RequestMapping(value = {"/properties"}, method = RequestMethod.GET, produces= MediaType.APPLICATION_JSON_UTF8_VALUE)
public Set<Map.Entry<Object, Object>> getProperties() {
return props.entrySet();
}
}
if you are Using spring-boot then add spring-actuator dependency which by defaults expose /env endpoint and spits out all the properties loaded in the spring container in json format.
I am trying to convert the XML message to JSON using camel router and save it into a file. Getting the XML message from the source and saving it to destination file etc are working. But when I try to convert to JSON, it did not work. I did not even throw any error/exception in logs. I am running on OSGI container
public class CamelRouter extends RouteBuilder {
#Override
public void configure() throws Exception {
from("file://C:/test/Sample.xml")
.routeId("file-to-file")
.log(LoggingLevel.INFO,"RouteID file-to-file !!!!! starting")
//From XML to JSON
.bean(CamelRouter.class, "convertXmlToJson")
.log(LoggingLevel.INFO,"From XML to JSON !!!!! Done")
.to("file://C:/test/JSONMessages")
.log(LoggingLevel.INFO,"Converted Message Saved successfully");
The bean method to convert XML to JSON convertXmlToJson is shown below
public String convertXmlToJson(String msg) {
log.info("NOW calling JSON conversion");
String jsonStr = null;
log.info("MESSAGE conversion starting : "); //After this message nothing happened
XMLSerializer xmlReader = new XMLSerializer();
log.info("MESSAGE before conversion : " + msg);
jsonStr = xmlReader.read(msg).toString();
log.info("JSON data : " + jsonObj.toString());
return jsonObj.toString();
}
Is anyone know why it is not executing the XMLSerializer portion. I tried this approach because the camel-xmljson's marshal().xmljson() call also give me the same results. Nothing happened after the xmljson() call in my camel routing.
Things that I checked are:
camel-xmljson feature up and running in OSGI
Dependencies mentioned in the Apache XmlJSON website added in my pom file, xom, camel-xmljson etc.
Am I missing anything here? Please help
The problem with your code route is that your bean component handler method resides within your route builder class, plus you invoke the bean component in a way that triggers another instantiation of that route builder class.
Personally, I would move convertXmlToJson to an appropriate utility class. That way you reduce mix of concern in the route builder and the bean component should work fine.
Alternatively, your route might work, if you invoke the bean component like this:
.bean(this, "convertXmlToJson")
I am passing a json object to the client side from java object with a time and value as attributes with gson
this.template.convertAndSend("/topic/123", gson.toJson(object, type));
and on the client side i have the following code where the json object data is stored in the body of the payload but I am unable to access the properties with obj.time or obj.value, it tells me undefined after it is parsed, I tried showing the entire 'obj' itself and the format seems fine however:
var subscription_callback1 = function(payload) {
var obj = JSON.parse(payload.body);
alert(obj);
};
output with alert(obj)
{"time":"3:00:34","value":"7989797"}
Nevermind solved. Since I am transfering STOMP protocol messages with the Spring 4 framework. I opted to use the Jackson2 message converter instead of directly using gson and it seems to work
#Configuration
#EnableWebSocketMessageBroker
public class MessageBrokerConfigurer extends AbstractWebSocketMessageBrokerConfigurer {
#Override
public boolean configureMessageConverters(List<MessageConverter> messageConverters) {
messageConverters.add(new MappingJackson2MessageConverter());
return true;
}
then i directly put my java object into the send function instead of using gson to convert it as above
this.template.convertAndSend("/topic/123", event)
I have a JAX-RS WebService with the following method:
#Path("/myrest")
public class MyRestResource {
...
#GET
#Path("/getInteger")
#Produces(APPLICATION_JSON)
public Integer getInteger() {
return 42;
}
When accessed using this snipped:
#Test
public void testGetPrimitiveWrapers() throws IOException {
// this works:
assertEquals(new Integer(42), new ObjectMapper().readValue("42", Integer.class));
// that fails:
assertEquals(new Integer(42), resource().path("/myrest/getInteger").get(Integer.class));
}
I get the following exception:
com.sun.jersey.api.client.ClientResponse getEntity
SEVERE: A message body reader for Java class java.lang.Integer, and Java type class java.lang.Integer, and MIME media type application/json was not found
com.sun.jersey.api.client.ClientResponse getEntity
SEVERE: The registered message body readers compatible with the MIME media type are: application/json
...
The problem is just with returning single primitive values (int/boolean) or their wrapper classes. Returning other POJO classes is not the problemen so I guess all the answers regarding JSONConfiguration.FEATURE_POJO_MAPPING and JAXB annotations do not apply here.
Or which annotation should I use to describe the return type if I don't have access to its
class source?
Using ngrep I can verify that just the String "42" is returned by the webservice. Thats a valid JSON "value" but not a valid JSON "text" according to the spec. So is my problem on the client or the server side?
I tried activating JSONConfiguration natural/badgerfish according to http://tugdualgrall.blogspot.de/2011/09/jax-rs-jersey-and-single-element-arrays.html but with no success (ngrep still shows just "42"). Would that be the right path?
Any ideas are appreciated!
This is a recognized bug in Jackson, which has been touted (incorrectly in my opinion) as a feature. Why do I consider it a bug? Because while serialization works, deserialization definitely does not.
In any case, valid JSON cannot be generated from your current return type, so I would recommend creating a wrapper class:
class Result<T> {
private T data;
// constructors, getters, setters
}
#GET
#Path("/getInteger")
#Produces(APPLICATION_JSON)
public Result<Integer> getInteger() {
return new Result<Integer)(42);
}
Alternatively, you can elect to wrap root values, which will automatically encapsulate your data in a top level JSON object, keyed by the objects simple type name - but note that if this option is used that all generated JSON will be wrapped (not just for primitives):
final ObjectMapper mapper = new ObjectMapper()
.configure(SerializationFeature.WRAP_ROOT_VALUE, true)
.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true);
final String serializedJson = mapper.writeValueAsString(42);
final Integer deserializedVal = mapper.readValue(serializedJson,
Integer.class);
System.out.println(serializedJson);
System.out.println("Deserialized Value: " + deserializedVal);
Output:
{"Integer":42}
Deserialized Value: 42
See this answer for details on how to retrieve and configure your ObjectMapper instance in a JAX-RS environment.