private String getEmailTemplateWithActualValueForAccount(String template, Account account) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
Map<String,String> map = new HashMap<String, String>();
List<String> listTags = new ArrayList<String>();
Map<Method, String> methodList = new HashMap<Method, String>();
int startIndex=0;
int endIndex=0;
for(int i=0; i<template.length(); i++)
{
char ch = template.charAt(i);
if(ch=='$')
startIndex = i+1;
if(ch=='#')
{
endIndex = i+1;
listTags.add(template.substring(startIndex,endIndex));
}
}
Method[] methods = Account.class.getMethods();
for (Method method : methods) {
String methodName = method.getName();
if(method.getName().startsWith("get"))
{
methodList.put(method, methodName.substring(3,methodName.length()).toUpperCase()+"#");
}
}
Set<Method> methodKeySet = methodList.keySet();
for (Method method : methodKeySet) {
for (String string : listTags) {
if(methodList.get(method).equals(string))
{
try{
Object obj = method.invoke(account, null);
if(obj!=null)
map.put(string, obj.toString());
}catch(NullPointerException e){
}
}
}
}
final StringBuilder list = new StringBuilder( "\\$(" );
for( final String key: map.keySet() )
{
list.append( key );
list.append( "|" );
}
list.append( "[^\\s\\S])" );
Pattern pattern = Pattern.compile( list.toString() );
Matcher matcher = pattern.matcher( template );
final StringBuffer stringBuffer = new StringBuffer();
while( matcher.find() ){
final String string = matcher.group( 1 );
matcher.appendReplacement( stringBuffer, map.get( string ));
}
matcher.appendTail( stringBuffer );
return stringBuffer.toString();
}
I got an exception at line of code "Object obj = method.invoke(account, null);"
Code is perfectly working but as this code is in scheduler it will create an log at every 20 second on jboss server.
The invoke method of Method throws an InvocationTargetException "if the underlying method throws an exception", according to the Javadoc. So you better look into the method that you are invoking to find out why it's throwing an exception. Check the exception stack trace for the root cause.
Instead of catching NullPointerException, you should catch InvocationTargetException, and check the wrapped exception.
Related
I would like to work on moving the json data from libgdx to my web server, but I am not sure how to do it. The method below was created by referring to libgdx's documentation.
private void httpPostJson(){
final Json json = new Json();
final String requestJson = json.toJson(requestObject);
Net.HttpRequest request = new Net.HttpRequest("POST");
final String url = "http://localhost:8080/data";
request.setUrl(url);
request.setContent(requestJson);
request.setHeader("Content-Type", "application/json");
Gdx.net.sendHttpRequest(request, new Net.HttpResponseListener() {
#Override
public void handleHttpResponse(Net.HttpResponse httpResponse) {
String responseJson = httpResponse.getResultAsString();
Gson gson = new Gson();
data = gson.fromJson(responseJson, Person.class);
//'Person' is just sample class. data is class Person's object.
data.StoreData("",1);//successed to receive json data from web server.
//StoreData is just getter method.
}
#Override
public void failed(Throwable t) {
Gdx.app.log("failed!");
}
#Override
public void cancelled() {
Gdx.app.log("cancelled!");
}
});
}
It is possible to receive data transmitted from a web server.
But, this method can't send data to web server.
Can you tell me how to move data from libgdx project to web server?
This is the data transmitted to the web server:
final String requestJson = json.toJson(requestObject);
We are using the following Code (as you have more control over the request as opposed to using gdx.net), works like a charm, just don't execute on the main thread - body is your JSON as String
URL url = new URL(<your url>);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setDoInput(true);
conn.setDoOutput(true);
conn.setRequestProperty("Accept", "application/json");
conn.setRequestProperty("Content-Type",
"application/json; charset=utf-8");
if (body != null) {
OutputStream os = conn.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(
os, "UTF-8"));
writer.write(body);
writer.close();
os.close();
}
conn.connect();
String s = stringFromStream(conn.getInputStream(), 4096);
Method stringFromStream:
public static String stringFromStream(final InputStream is,
final int bufferSize) {
final char[] buffer = new char[bufferSize];
final StringBuilder out = new StringBuilder();
try {
final Reader in = new InputStreamReader(is, "UTF-8");
try {
for (; ; ) {
int rsz = in.read(buffer, 0, buffer.length);
if (rsz < 0)
break;
out.append(buffer, 0, rsz);
}
} finally {
in.close();
}
} catch (Exception ex) {
}
return out.toString();
}
Please recommend the optimal approach for parsing urlencoded or JSON-encoded responses when using Jetty HttpClient.
For example, I have created the following utility class for sending ADM-messages and use BufferingResponseListener there, with UrlEncoded.decodeUtf8To (for parsing bearer token response) and JSON.parse (for parsing message sending response):
private final HttpClient mHttpClient;
private final String mTokenRequest;
private String mAccessToken;
private long mExpiresIn;
public Adm(HttpClient httpClient) {
mHttpClient = httpClient;
MultiMap<String> params = new MultiMap<>();
params.add("grant_type", "client_credentials");
params.add("scope", "messaging:push");
params.add("client_id", "amzn1.application-oa2-client.XXXXX");
params.add("client_secret", "XXXXX");
mTokenRequest = UrlEncoded.encode(params, null, false);
}
private final BufferingResponseListener mMessageListener = new BufferingResponseListener() {
#Override
public void onComplete(Result result) {
if (!result.isSucceeded()) {
if (result.getResponse().getStatus() % 100 == 4) {
String jsonStr = getContentAsString(StandardCharsets.UTF_8);
Map<String, String> resp = (Map<String, String>) JSON.parse(jsonStr);
String reason = resp.get("reason");
if ("AccessTokenExpired".equals(reason)) {
postToken();
} else if ("Unregistered".equals(reason)) {
// delete the invalid ADM registration id from the database
}
}
return;
}
String jsonStr = getContentAsString(StandardCharsets.UTF_8);
Map<String, String> resp = (Map<String, String>) JSON.parse(jsonStr);
String oldRegistrationId = (String) result.getRequest().getAttributes().get("registrationID");
String newRegistrationId = resp.get("registrationID");
if (newRegistrationId != null && !newRegistrationId.equals(oldRegistrationId)) {
// update the changed ADM registration id in the database
}
}
};
private final BufferingResponseListener mTokenListener = new BufferingResponseListener() {
#Override
public void onComplete(Result result) {
if (result.isSucceeded()) {
String urlencodedStr = getContentAsString(StandardCharsets.UTF_8);
MultiMap<String> params = new MultiMap<>();
UrlEncoded.decodeUtf8To(urlencodedStr, params);
long now = System.currentTimeMillis() / 1000;
mExpiresIn = now + Long.parseLong(params.getString("expires_in"));
mAccessToken = params.getString("access_token");
}
}
};
public void postMessage(String registrationId, int uid, String jsonStr) {
long now = System.currentTimeMillis() / 1000;
if (mAccessToken == null || mAccessToken.length() < 32 || mExpiresIn < now) {
postToken();
return;
}
mHttpClient.POST(String.format("https://api.amazon.com/messaging/registrations/%1$s/messages", registrationId))
.header(HttpHeader.ACCEPT, "application/json")
.header(HttpHeader.CONTENT_TYPE, "application/json")
.header(HttpHeader.AUTHORIZATION, "Bearer " + mAccessToken)
.header("X-Amzn-Type-Version", "com.amazon.device.messaging.ADMMessage#1.0")
.header("X-Amzn-Accept-Type", "com.amazon.device.messaging.ADMSendResult#1.0")
.attribute("registrationID", registrationId)
.content(new StringContentProvider(jsonStr))
.send(mMessageListener);
}
private void postToken() {
mHttpClient.POST("https://api.amazon.com/auth/O2/token")
.header(HttpHeader.ACCEPT, "application/json")
.header(HttpHeader.CONTENT_TYPE, "application/x-www-form-urlencoded")
.content(new StringContentProvider(mTokenRequest))
.send(mTokenListener);
}
The above class works okay, but seeing that there are Jetty-methods with InputStream in arguments, like
UrlEncoded.decodeTo(java.io.InputStream in, MultiMap map, java.lang.String charset, int maxLength, int maxKeys)
and
JSON.parse(java.io.InputStream in)
I wonder if there is a smarter way to fetch and parse... maybe with something more effective than BufferingResponseListener?
In other words my question is please:
How to use the "streaming" version of the above parsing methods with HttpClient?
I have a controller action Export which accepts a List of models like below. This is sending back and manipulated dataset back from the view where the user could interact with it. So we have been able to send the data down with much more information.
[HttpPost]
public JsonResult Export(List<MappingExportModel> sources){}
This works fine in all cases but there is one where we have a bigger than normal dataset. This is causing an issue with the export. So far I have tried just passing the values as an object or string but I am unable to convert them into any usable instance after the data is into the controller.
Is it possible to preemptively increase this maxjsonlength value somewhere. The value from the web.config is being ignored from what I have come across so far.
The error I receive is
"Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property"
I need to be able to accept this directly from the ajax request into the controller action. Spinning up a version of JsonResult and then setting the max value will not work because the error is thrown the the data is trying to be deserialized into the object var presented above. We get the value in the original GET request and do set the value before the view is loaded. Now we are taking the data from this view and sending it back plus all the manipulations the users have created.
User posts data to server, the controller action is hit with the data. The error is encountered and spit back out to the browser which handles the error.
You can use custom json length. add the following file in your project and edit your global.asax.cs
Global.asax
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
///// **********
JsonValueProviderFactory jsonValueProviderFactory = null;
foreach (var factory in ValueProviderFactories.Factories)
{
if (factory is JsonValueProviderFactory)
{
jsonValueProviderFactory = factory as JsonValueProviderFactory;
}
}
//remove the default JsonVAlueProviderFactory
if (jsonValueProviderFactory != null) ValueProviderFactories.Factories.Remove(jsonValueProviderFactory);
//add the custom one
ValueProviderFactories.Factories.Add(new CustomJsonValueProviderFactory());
/////*************
}
}
///******** for json length
public sealed class CustomJsonValueProviderFactory : ValueProviderFactory
{
private static void AddToBackingStore(Dictionary<string, object> backingStore, string prefix, object value)
{
IDictionary<string, object> d = value as IDictionary<string, object>;
if (d != null)
{
foreach (KeyValuePair<string, object> entry in d)
{
AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
}
return;
}
IList l = value as IList;
if (l != null)
{
for (int i = 0; i < l.Count; i++)
{
AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
}
return;
}
// primitive
backingStore[prefix] = value;
}
private static object GetDeserializedObject(ControllerContext controllerContext)
{
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
{
// not JSON request
return null;
}
StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
string bodyText = reader.ReadToEnd();
if (String.IsNullOrEmpty(bodyText))
{
// no JSON data
return null;
}
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.MaxJsonLength = int.MaxValue; //increase MaxJsonLength. This could be read in from the web.config if you prefer
object jsonData = serializer.DeserializeObject(bodyText);
return jsonData;
}
public override IValueProvider GetValueProvider(ControllerContext controllerContext)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
object jsonData = GetDeserializedObject(controllerContext);
if (jsonData == null)
{
return null;
}
Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
AddToBackingStore(backingStore, String.Empty, jsonData);
return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
}
private static string MakeArrayKey(string prefix, int index)
{
return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
}
private static string MakePropertyKey(string prefix, string propertyName)
{
return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
}
}
JsonValueProviderFactory.cs
public sealed class JsonValueProviderFactory : ValueProviderFactory
{
private static void AddToBackingStore(Dictionary<string, object> backingStore, string prefix, object value)
{
IDictionary<string, object> d = value as IDictionary<string, object>;
if (d != null)
{
foreach (KeyValuePair<string, object> entry in d)
{
AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
}
return;
}
IList l = value as IList;
if (l != null)
{
for (int i = 0; i < l.Count; i++)
{
AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
}
return;
}
// primitive
backingStore[prefix] = value;
}
private static object GetDeserializedObject(ControllerContext controllerContext)
{
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
{
// not JSON request
return null;
}
StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
string bodyText = reader.ReadToEnd();
if (String.IsNullOrEmpty(bodyText))
{
// no JSON data
return null;
}
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.MaxJsonLength = int.MaxValue; //increase MaxJsonLength. This could be read in from the web.config if you prefer
object jsonData = serializer.DeserializeObject(bodyText);
return jsonData;
}
public override IValueProvider GetValueProvider(ControllerContext controllerContext)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
object jsonData = GetDeserializedObject(controllerContext);
if (jsonData == null)
{
return null;
}
Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
AddToBackingStore(backingStore, String.Empty, jsonData);
return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
}
private static string MakeArrayKey(string prefix, int index)
{
return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
}
private static string MakePropertyKey(string prefix, string propertyName)
{
return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
}
}
by this you can pass lengthy json through ajax to controller and if you want to retrieve a lengthy string back to ajax result from controller then add below code in your controller also
//add this for getting large json string
protected override JsonResult Json(object data, string contentType, System.Text.Encoding contentEncoding, JsonRequestBehavior behavior)
{
return new JsonResult()
{
Data = data,
ContentType = contentType,
ContentEncoding = contentEncoding,
JsonRequestBehavior = behavior,
MaxJsonLength = Int32.MaxValue
};
}
I am trying to combine two kafka topics using the a single kafka consumer on a list of topics, further convert the json string in the stream to POJO. Then, join them via keyBy ( On event time field ) and to merge them as a single fat json, I was planning to use a window stream and apply a window function on the window stream. The assumption is that Topic-A & Topic-B can be joined on Event Time and only one pair ( Topic A ( JSON ) , Topic B (JSON ) will be present with the same eventTime. Hence was planning to use a coutWindow(2) post keyBy on eventTime.
I have couple of questions for the same;
Is the approach fine for merging topics and creating a single JSON?
The window function on All Window stream doesnt seem to work fine; Any pointers will be greatly appreciated.
Code Snippet :
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
logger.info("Flink Stream Window Charger has started");
Properties properties = new Properties();
properties.setProperty("bootstrap.servers", "127.0.0.1:1030");
properties.setProperty("zookeeper.connect", "127.0.0.1:2181/service-kafka");
properties.setProperty("group.id", "group-0011");
properties.setProperty("auto.offset.reset", "smallest");
List < String > names = new ArrayList < > ();
names.add("Topic-A");
names.add("Topic-B");
DataStream < String > stream = env.addSource(new FlinkKafkaConsumer08 < > (names, new SimpleStringSchema(), properties));
DataStream < TopicPojo > pojo = stream.map(new Deserializer()).keyBy((eventTime) -> TopicPojo.getEventTime());
List < String > where = new ArrayList < String > ();
AllWindowedStream < String, GlobalWindow > data_window = pojo.flatMap(new Tokenizer()).countWindowAll(2);
DataStream < String > data_charging = data_window.apply(new MyWindowFunction());
data_charging.addSink(new SinkFunction < String > () {
public void invoke(String value) throws Exception {
// Yet to be implemented - Merge two POJO into one
}
});
try
{
env.execute();
} catch (Exception e)
{
return;
}
}
}
class Tokenizer implements FlatMapFunction < TopicPojo, String > {
private static final long serialVersionUID = 1 L;
#Override
public void flatMap(TopicPojo value, Collector < String > out) throws Exception {
ObjectMapper mapper = new ObjectMapper();
out.collect(mapper.writeValueAsString(value));
}
}
class MyWindowFunction implements WindowFunction < TopicPojo, String, String, GlobalWindow > {
#Override
public void apply(String key, GlobalWindow window, Iterable < TopicPojo > arg2, Collector < String > out)
throws Exception {
int count = 0;
for (TopicPojo in : arg2) {
count++;
}
// Test Result - TO be modified
out.collect("Window: " + window + "count: " + count);
}
}
class Deserializer implements MapFunction < String, TopicPojo > {
private static final long serialVersionUID = 1 L;
#Override
public TopicPojo map(String value) throws IOException {
// TODO Auto-generated method stub
ObjectMapper mapper = new ObjectMapper();
TopicPojo obj = null;
try {
System.out.println(value);
obj = mapper.readValue(value, TopicPojo.class);
} catch (JsonParseException e) {
// TODO Auto-generated catch block
throw new IOException("Failed to deserialize JSON object.");
} catch (JsonMappingException e) {
// TODO Auto-generated catch block
throw new IOException("Failed to deserialize JSON object.");
} catch (IOException e) {
// TODO Auto-generated catch block
throw new IOException("Failed to deserialize JSON object.");
}
return obj;
}
}
I am getting -
The method apply(AllWindowFunction) in the type AllWindowedStream is not applicable for the arguments (MyWindowFunction) error.
An AllWindowedStream is a non-keyed stream, and so the apply method for AllWindowedStreams doesn't have a key parameter. Since you are windowing a keyed stream, your data_window should be a KeyedStream.
I can't seem to find out how to serialize Hibernate's implementation of constraint violations using Gson.
Here's what I've tried so far.
Approach 1
MyPojo aPojo = new MyPojo();
Gson gson = new Gson();
Set<ConstraintViolation<MyPojo>> violations = validator.validate(aPojo);
System.out.println(gson.toJson(violations));
Fails with this error:
java.lang.UnsupportedOperationException:
Attempted to serialize java.lang.Class: com.bar.baz.MyPojo.
Forgot to register a type adapter?
at com.google.gson.internal.bind.TypeAdapters$1.write(TypeAdapters.java:67)
at com.google.gson.internal.bind.TypeAdapters$1.write(TypeAdapters.java:61)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:89)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:195)
at com.google.gson.internal.bind.ObjectTypeAdapter.write(ObjectTypeAdapter.java:107)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:96)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:60)
at com.google.gson.Gson.toJson(Gson.java:593)
at com.google.gson.Gson.toJson(Gson.java:572)
at com.google.gson.Gson.toJson(Gson.java:527)
at com.google.gson.Gson.toJson(Gson.java:507)
Approach 2
Gson gson = new Gson();
Set<ConstraintViolation<MyPojo>> violations = validator.validate(MyPojo);
System.out.println(
gson.toJson(violations,
new TypeToken<ConstraintViolation<MyPojo>>() {}.getType())
);
Fails by not serializing MyPojo's properties:
Output: {}.
Approach 3
I was expecting this approach to delegate serialization to my custom Serializer but it still fails:
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(
new TypeToken<ConstraintViolation<MyPojo>>() {}.getType(),
new JsonSerializer<ConstraintViolation<MyPojo>>() {
#Override
public JsonElement serialize(ConstraintViolation<MyPojo> src, Type typeOfSrc, JsonSerializationContext context) {
JsonObject result = new JsonObject();
result.addProperty("aTestProperty", "A Test Value");
return result;
}
});
Gson gson = builder.create();
Set<ConstraintViolation<MyPojo>> violations = validator.validate(MyPojo);
System.out.println(gson.toJson(violations));
However it fails with this error:
java.lang.UnsupportedOperationException:
Attempted to serialize java.lang.Class:
com.bar.baz.MyPojo.
Forgot to register a type adapter?
at com.google.gson.internal.bind.TypeAdapters$1.write(TypeAdapters.java:67)
at com.google.gson.internal.bind.TypeAdapters$1.write(TypeAdapters.java:61)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:89)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:195)
at com.google.gson.internal.bind.ObjectTypeAdapter.write(ObjectTypeAdapter.java:107)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:96)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:60)
at com.google.gson.Gson.toJson(Gson.java:593)
at com.google.gson.Gson.toJson(Gson.java:572)
at com.google.gson.Gson.toJson(Gson.java:527)
at com.google.gson.Gson.toJson(Gson.java:507)
Approach 4
Looking at the error message, I though this might work:
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(
new TypeToken<ConstraintViolation<MyPojo>>() {}.getType(),
new JsonSerializer<ConstraintViolation<MyPojo>>() {
#Override
public JsonElement serialize(ConstraintViolation<MyPojo> src, Type typeOfSrc, JsonSerializationContext context) {
JsonObject result = new JsonObject();
result.addProperty("aTestProperty", "A Test Value");
return result;
}
});
builder.registerTypeAdapter(
new TypeToken<MyPojo>() {}.getType(),
new JsonSerializer<MyPojo>() {
#Override
public JsonElement serialize(MyPojo src, Type typeOfSrc, JsonSerializationContext context) {
JsonObject result = new JsonObject();
result.addProperty("anotherTestProperty", "Another Test Value");
return result;
}
});
Gson gson = builder.create();
Set<ConstraintViolation<MyPojo>> violations = validator.validate(MyPojo);
System.out.println(gson.toJson(violations));
But it fails with a similar error.
Approach 5: Working but ugly
The only thing that I've managed to make work is to register the serializer with the type of the vendor (Hibernate) specific implementation for ConstraintViolation:
Set<ConstraintViolation<MyPojo>> violations = validator.validate(MyPojo);
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(
new TypeToken<ConstraintViolationImpl>() {}.getType(),
new JsonSerializer<ConstraintViolation<MyPojo>>() {
#Override
public JsonElement serialize(ConstraintViolation<MyPojo> src, Type typeOfSrc, JsonSerializationContext context) {
JsonObject result = new JsonObject();
result.addProperty("aTestProperty", "A Test Value");
return result;
}
});
Gson gson = builder.create();
System.out.println(gson.toJson(violations));
Is there a way to make this work without relying on the concrete implementation of ConstraintViolation (i.e. org.hibernate.validator.internal.engine.ConstraintViolationImpl)?
There doesn't seem to be a reasonable approach to serialize javax.validation.ConstraintViolation objects. In fact, even Jackson errs while trying to serialize the set:
Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: fromIndex(0) > toIndex(-1) (through reference chain: java.util.HashSet[0]->org.hibernate.validator.internal.engine.ConstraintViolationImpl["propertyPath"]->org.hibernate.validator.internal.engine.path.PathImpl["pathWithoutLeafNode"]->org.hibernate.validator.internal.engine.path.PathImpl["pathWithoutLeafNode"]->org.hibernate.validator.internal.engine.path.PathImpl["pathWithoutLeafNode"])
at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:232)
For the time being, I just convert the set of errors into a set of custom POJOs I've written and serialize that instead.
Custom ValidationError POJO:
public class ValidationError {
private String className;
private String propertyPath;
private String errorMessage;
public static Set<ValidationError> fromViolations(Set violations) {
Set<ValidationError> errors = new HashSet<ValidationError>();
for (Object o : violations) {
ConstraintViolation v = (ConstraintViolation) o;
ValidationError error = new ValidationError();
error.setClassName(v.getRootBeanClass().getSimpleName());
error.setErrorMessage(v.getMessage());
error.setPropertyPath(v.getPropertyPath().toString());
errors.add(error);
}
return errors;
}
public String getClassName() {
return className;
}
public void setClassName(String className) {
this.className = className;
}
public String getPropertyPath() {
return propertyPath;
}
public void setPropertyPath(String propertyPath) {
this.propertyPath = propertyPath;
}
public String getErrorMessage() {
return errorMessage;
}
public void setErrorMessage(String errorMessage) {
this.errorMessage = errorMessage;
}
#Override
public String toString() {
return "ValidationError{" +
"className='" + className + '\'' +
", propertyPath='" + propertyPath + '\'' +
", errorMessage='" + errorMessage + '\'' +
'}';
}
}
Sample usage:
Set<ConstraintViolation<MyBean>> violations = validator.validate(myBean);
Set<ValidationError> errors = ValidationError.fromViolations(violations);
GsonBuilder gsonBuilder = new GsonBuilder();
Gson gson = gsonBuilder.create();
System.out.println(gson.toJson(errors));
Update
For the sake of record, it is worth mentioning that XStream can serialize the set of constraint violations like a charm:
XStream xstream = new XStream(new JettisonMappedXmlDriver());
xstream.setMode(XStream.NO_REFERENCES);
System.out.println(xstream.toXML(violations));
However the generated the object graph is way too much verbose and is not suitable for use in production anyway. You can see the sample output here.