Jersey Exception SEVERE A message body reader for Java class

Question

I have a Jersey based Rest WS which outputs JSON  I am implementing a Jersey Client to invoke the WS and consume the JSON response  The client code I have is below   WebResource r   restClient resource UriBuilder fromUri  http   localhost    port 8080  build     String resp   r path   user   accept MediaType APPLICATION JSON  get String class   User   users   r path   user   accept MediaType APPLICATION JSON  get User   class     The 2nd line outputs the JSON string response correctly  however the 3rd line to marshal JSON to the POJO is not happening and I get the following exception stacktrace   SEVERE  A message body reader for Java class  Lorg shoppingsite model entity jpa User   and Java type class  Lorg shoppingsite model entity jpa User   and MIME media type application json was not found Dec 21  2011 11 32 01 AM com sun jersey api client ClientResponse getEntity SEVERE  The registered message body readers compatible with the MIME media type are      -    com sun jersey core impl provider entity FormProvider   com sun jersey core impl provider entity StringProvider   com sun jersey core impl provider entity ByteArrayProvider   com sun jersey core impl provider entity FileProvider   com sun jersey core impl provider entity InputStreamProvider   com sun jersey core impl provider entity DataSourceProvider   com sun jersey core impl provider entity XMLJAXBElementProvider General   com sun jersey core impl provider entity ReaderProvider   com sun jersey core impl provider entity DocumentProvider   com sun jersey core impl provider entity SourceProvider StreamSourceReader   com sun jersey core impl provider entity SourceProvider SAXSourceReader   com sun jersey core impl provider entity SourceProvider DOMSourceReader   com sun jersey core impl provider entity XMLRootElementProvider General   com sun jersey core impl provider entity XMLListElementProvider General   com sun jersey core impl provider entity XMLRootObjectProvider General   com sun jersey core impl provider entity EntityHolderReader   I have the correct MIME TYPES in my request  My POJO has been annotated with XMLRootElement  What am I missing    Thank you

User · Answer

If you are building an uberjar or  shaded jar   make sure your meta inf service files are merged    This bit me multiple times on a dropwizard project    If you are using the gradle shadowJar plugin  you want to call mergeServiceFiles   in your shadowJar target  https   github com johnrengelman shadow merging-service-files  Not sure what the analogous commands are for maven or other build systems

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You need to implement your own MessageBodyReader and MessageBodyWriter for your class Lorg shoppingsite model entity jpa User    package javax ws rs ext   import java io IOException  import java io InputStream  import java lang annotation Annotation  import java lang reflect Type  import javax ws rs WebApplicationException  import javax ws rs core MediaType  import javax ws rs core MultivaluedMap   public interface MessageBodyReader lt T extends Object gt         public boolean isReadable Class lt   gt  type           Type genericType           Annotation   annotations           MediaType mediaType        public T readFrom Class lt T gt  type           Type genericType           Annotation   annotations           MediaType mediaType           MultivaluedMap lt String  String gt  httpHeaders           InputStream entityStream  throws IOException  WebApplicationException     package javax ws rs ext   import java io IOException  import java io OutputStream  import java lang annotation Annotation  import java lang reflect Type  import javax ws rs WebApplicationException  import javax ws rs core MediaType  import javax ws rs core MultivaluedMap   public interface MessageBodyWriter lt T extends Object gt         public boolean isWriteable Class lt   gt  type           Type genericType           Annotation   annotations           MediaType mediaType        public long getSize T t           Class lt   gt  type           Type genericType           Annotation   annotations           MediaType mediaType        public void writeTo T t           Class lt   gt  type           Type genericType           Annotation   annotations           MediaType mediaType           MultivaluedMap lt String  Object gt  httpHeaders           OutputStream entityStream  throws IOException  WebApplicationException

User · Answer

I was able to fix the issue by adding the maven dependency for jersey-json

User · Answer

Some may be confused why add jersey-json jar can t solve this problem  I found out that this jar has to newer than jersey-json-1 7 jar  1 7 0 doesn t work  but 1 7 1 works fine    hope this can help

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Just check if you are running different instances in eclipse  I quit all my other sessions  clean build fixed the problem

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Mine was similar situation  I get this error in crucial times and I did not remember how I had solved it before  which I did many number of times  After strenuous hours of inspection  I have solved and reproduced the error and made sure how simple is the solution for this situation    Okay - solution   remove  or correct  any newly made changes to your main project s properties files   Yes  this is it  In fact  my project is a multi-moduled huge one  and you know going without correct dependencies is a rare case scenario as is fetched often from git  RAC too   My project was getting almost all configurable things from a properties file that is common to about 15 or so modules  sub projects  with good amount of intra-dependencies among them  jersey-json s dependency is always there in my merged parent pom  XML Annotations aren t a problem as the project is being run for around 100 times after modifying them  some solutions here point to web xml and things like POJOMappingFeature  In my case  I haven t even touched the webapp module in this build  so anyhow  this solution worked for me and I am spending time to record this in SO in case if I ever happen to fall into this error  I would not have to waste my sleepy nights   of course  for you too

User · Answer

Just add below lines in your POJO before start of class  and your issue is resolved        Produces  application json         XmlRootElement      See example       import javax ws rs Produces       import javax xml bind annotation XmlRootElement            author manoj kumar     email kumarmanoj mtech gmail com       Produces  application json     XmlRootElement    public class User     private String username   private String password   private String email   public String getUsername      return username      public void setUsername String username         this username   username      public String getPassword          return password      public void setPassword String password         this password   password      public String getEmail         return email      public void setEmail String email        this email   email        add below lines inside of your web xml  lt init-param gt       lt param-name gt com sun jersey api json POJOMappingFeature lt  param-name gt       lt param-value gt true lt  param-value gt   lt  init-param gt    Now recompile your webservice everything would work

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We also decided to use jersey as a solution  But as we are using org JSON in most of the cases this dependency is unecessary and we felt not good    Therefore we used the String representation to get a org JSON object  instead of  JSONObject output   response getEntity JSONObject class      we use it this way now    JSONObject output   new JSONObject response getEntity String class       where JSONObject comes from org JSON and the imports could be changed from   -import org codehaus jettison json JSONArray  -import org codehaus jettison json JSONException  -import org codehaus jettison json JSONObject   import org json JSONArray   import org json JSONException   import org json JSONObject

User · Answer

Try adding    lt dependency gt       lt groupId gt com owlike lt  groupId gt       lt artifactId gt genson lt  artifactId gt       lt version gt 1 4 lt  version gt   lt  dependency gt    Also this problem may occur if you re using HTTP GET with message body so in this case adding jersey-json lib   XmlRootElement or modifying web xml won t help  You should use URL QueryParam or HTTP POST

User · Answer

To make it work you only need two things  Check if you are missing    First of all  you need  XmlRootElement annotation for your object class entity  You need to add dependency for jersey-json if you are missing For your reference I added this dependency into my pom xml    lt dependency gt       lt groupId gt com sun jersey lt  groupId gt       lt artifactId gt jersey-json lt  artifactId gt       lt version gt 1 17 1 lt  version gt   lt  dependency gt

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In my case  I m using POJO  And I forgot configure POJOMappingFeature as true  Maycon has pointed it out in an early answer  However some guys might have trouble to configure it in web xml correctly  here is my example    lt servlet gt       lt servlet-name gt Jersey Servlet lt  servlet-name gt       lt servlet-class gt com sun jersey spi spring container servlet SpringServlet lt  servlet-class gt       lt init-param gt           lt param-name gt com sun jersey api json POJOMappingFeature lt  param-name gt           lt param-value gt true lt  param-value gt       lt  init-param gt       lt load-on-startup gt 1 lt  load-on-startup gt   lt  servlet gt

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just put this       lt init-param gt           lt param-name gt com sun jersey api json POJOMappingFeature lt  param-name gt           lt param-value gt true lt  param-value gt       lt  init-param gt

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Q  Code was working fine in Intellj but failing in command line   Sol  Add dependencies of jersey as a direct dependency rather than a transient one   Reasoning  Since  it was working fine with IntelliJ  dependencies are correctly configured     Get required dependencies by one of the following    check for the IntelliJ running command  Stackoverflow-link List dependencies from maven mvn dependency tree  Now  add those problematic jersey dependencies explicitly

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for Python and Swagger example   import requests base url    https   petstore swagger io v2  def store order uid       api url   f  base url  store order      api data              id  uid           petId   0           quantity   0           shipDate    2020-04-08T07 56 05 832Z            status    placed            complete    true                  is a kind of magic       r   requests post api url  json api data      return r print store order 0  content        Most important string with MIME type  r   requests post api url  json api data

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I know that this post is old and you figured this out a long time ago  but just to save the people who will read this some time   You probably forgot to add annotation to the entity you are passing to the endpoint  so Jersey does not know how to process the POJO it receives  Annotate the pojo with something like this     XmlRootElement name    someName

[java] Jersey Exception : SEVERE: A message body reader for Java class

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