Jackson JSON + Java Generics get LinkedHashMap

Question

I have a question which is similar to some questions at stackoverflow but none really answer my problem. I use the ObjectMapper of Jackson and want to parse this JSON string into an List of User objects:

[{ "user" : "Tom", "role" : "READER" },   { "user" : "Agnes", "role" : "MEMBER" }] 

I define an inner class like this:

public class UserRole {      private String user     private String role;      public void setUser(String user) {         this.user = user;     }      public void setRole(String role) {         this.role = role;     }      public String getUser() {         return user;     }      public String getRole() {         return role;     } } 

To parse the JSON String to an List of UserRoles I use generics:

protected <T> List<T> mapJsonToObjectList(String json) throws Exception {     List<T> list;     try {         list = mapper.readValue(json, new TypeReference<List<T>>() {});     } catch (Exception e) {         throw new Exception("was not able to parse json");     }     return list; } 

But what I get back is a List of LinkedHashMaps.

What is wrong with my code?

Answer 1

The following works and as per StaxMan's advice no longer uses the deprecated static collectionType() method.

public class SoApp {     /**     * @param args     * @throws Exception     */    public static void main(String[] args) throws Exception    {       System.out.println("Hello World!");        String s = "[{\"user\":\"TestCity\",\"role\":\"TestCountry\"},{\"user\":\"TestCity\",\"role\":\"TestCountry\"}]";       StringReader sr = new StringReader("{\"user\":\"TestCity\",\"role\":\"TestCountry\"}");       //UserRole user = mapper.readValue(sr, UserRole.class);        mapJsonToObjectList(s,UserRole.class);     }     protected static <T> List<T> mapJsonToObjectList(String json, Class<T> clazz) throws Exception    {       List<T> list;       ObjectMapper mapper = new ObjectMapper();       System.out.println(json);       TypeFactory t = TypeFactory.defaultInstance();       list = mapper.readValue(json, t.constructCollectionType(ArrayList.class,clazz));        System.out.println(list);       System.out.println(list.get(0).getClass());       return list;    } } 

...

public class UserRole{     private String user;    private String role;     public void setUser(String user) {        this.user = user;    }     public void setRole(String role) {        this.role = role;    }     public String getUser() {        return user;    }     public String getRole() {        return role;    }     @Override    public String toString()    {       return "UserRole [user=" + user + ", role=" + role + "]";    }     } 

output...

 Hello World! [{"user":"TestCity","role":"TestCountry"},{"user":"TestCity","role":"TestCountry"}] [UserRole [user=TestCity, role=TestCountry], UserRole [user=TestCity, role=TestCountry]] class com.test.so.fix.UserRole