Converting json to object

Question

I am trying to convert the below json into a java bean, and need your help

Sort.json

{
 "messages": [
 {
 "GG_RETAIL_BRANCH_SAVING_SELLER": [
 "hello jackson 1",
 "hello jackson 2",
 "hello jackson 3"
 ]
 },
 {
 "GG_RETAIL_CONNECT_SAVINGS_SELLER": [
 "hello jackson 4",
 "hello jackson 5",
 "hello jackson 6"
 ]
 }
 ]
}

My Bean looks like

import java.io.Serializable;
import java.util.List;
import java.util.Map;
public class Sort implements Serializable{
 /**
 * 
 */
 private static final long serialVersionUID = 8122222228160190915L;
 /* private String name;
 private int age;*/
 private Map<String,List<String>> messages;
 @Override
 public String toString() {
 return "AdamSort [messages=" + messages + "]";
 }
 public Map<String, List<String>> getMessages() {
 return messages;
 }
 public void setMessages(Map<String, List<String>> messages) {
 this.messages = messages;
 }
}

And my test class is

import java.io.File;
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
public class JacksonExample {
 /**
 * @param args
 */
 public static void main(String[] args) {
 ObjectMapper mapper = new ObjectMapper();
 try { 
 Sort sort = mapper.readValue(new File("C:\\Sort.json"), Sort.class);
 System.out.println(sort);
 } catch (JsonGenerationException e) {
 e.printStackTrace();
 } catch (JsonMappingException e) {
 e.printStackTrace();
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
}

The error I see is

org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.util.LinkedHashMap out of START_ARRAY token
 at [Source: C:\Sort.json; line: 2, column: 3] (through reference chain: com.test.Sort["messages"])
 at org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:163)
 at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:219)
 at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:212)
 at org.codehaus.jackson.map.deser.std.MapDeserializer.deserialize(MapDeserializer.java:246)
 at org.codehaus.jackson.map.deser.std.MapDeserializer.deserialize(MapDeserializer.java:33)
 at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:299)
 at org.codehaus.jackson.map.deser.SettableBeanProperty$MethodProperty.deserializeAndSet(SettableBeanProperty.java:414)
 at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:697)
 at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580)
 at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2732)
 at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1817)
 at com.test.util.JacksonExample.main(JacksonExample.java:28)

Please suggest:

• PKey: Possible duplicate of Can not deserialize instance of java.util.HashMap out of START_ARRAY token
• Saurabh Jhunjhunwala: They are only using a list, but I have a Map<String,List<String>>, I can accept its similar, but that solution does not seem to work
• SF..MJ: check onces ObjectMapper mapper = new ObjectMapper(); Map<String,List<Map<String, Object>>> data = mapper.readValue(json, new TypeReference<Map<String,List<Map<String, Object>>>>(){});

Answer 1

While Looking at JSON string , messages are the list of Map .

Replace Map<String,List<String>> with List<Map<String, List<String>>> in Sort.java and give a try .

• Saurabh Jhunjhunwala: I think I have a simpler solution. The complex the data-structure, the complex it is for Jackson to map.

Answer 2

Your JSON translates to something like:

public class Sort {
 private List<Message> messages;
}
public class Message {
 private List<String> GG_RETAIL_BRANCH_SAVING_SELLER;
}

So you can either use such classes, or write a custom deserializer for jackson.

UPDATE:

OK, try with a deserializer:

 ObjectMapper mapper = new ObjectMapper();
 try {
 SimpleModule module = new SimpleModule();
 module.addDeserializer(Sort.class, new SortDeserializer());
 mapper.registerModule(module);

Here's the class SortDeserializer:

public class SortDeserializer extends StdDeserializer<Sort> {
 public SortDeserializer() { 
 this(null); 
 } 
 public SortDeserializer(Class<?> vc) { 
 super(vc); 
 }
 @Override
 public Sort deserialize(JsonParser jp, DeserializationContext dc)
 throws IOException, JsonProcessingException {
 Map<String,List<String>> messages = new HashMap<>();
 JsonNode node = jp.getCodec().readTree(jp);
 ArrayNode msgs = (ArrayNode)node.get("messages");
 for (JsonNode parm: msgs) {
 for (Iterator<String> it = parm.fieldNames(); it.hasNext(); ) {
 String key = it.next();
 ArrayNode values = (ArrayNode)parm.get(key);
 List<String> list = new ArrayList<>();
 for (JsonNode vnode: values) {
 list.add(vnode.asText());
 }
 messages.put(key, list);
 }
 }
 Sort resp = new Sort();
 resp.setMessages(messages);
 return resp;
 } 
}

• Saurabh Jhunjhunwala: If you look at my json, I have multiple keys, like "GG_RETAIL_BRANCH_SAVING_SELLER " & "GG_RETAIL_CONNECT_SAVINGS_SELLER".. If I only use " GG_RETAIL_BRANCH_SAVING_SELLER " that means I would also need one for "GG_RETAIL_CONNECT_SAVINGS_SELLER" and all sub-sequent , which is not quite optimal.
• Maurice Perry: @SaurabhJhunjhunwala OK, sorry, I have misread the JSON, so forget the Message class.

Answer 3

The java bean is incorrect in accordance with the json . It should be:

import java.util.ArrayList;
import java.util.Map;
public class Sort {
 ArrayList<Map<String,ArrayList<String>>> messages;
 public ArrayList<Map<String, ArrayList<String>>> getMessages() {
 return messages;
 }
 public void setMessages(ArrayList<Map<String, ArrayList<String>>> messages) {
 this.messages = messages;
 }
}

Answer 4

Modified the JSON a bit

{
 "messages": [
 {
 "group": "GG_RETAIL_BRANCH_SAVING_SELLER",
 "sortCode": [
 "hello jackson 1",
 "hello jackson 2",
 "hello jackson 3"
 ]
 },
 {
 "group": "GG_RETAIL_BRANCH_SAVING_SELLER",
 "sortCode": [
 "hello jackson 4",
 "hello jackson 5",
 "hello jackson 6"
 ]
 }
 ]
}

Added a new class :

import java.util.List;
public class Message {
 private String group;
 private List<String> sortCode;
 public String getGroup() {
 return group;
 }
 public void setGroup(String group) {
 this.group = group;
 }
 public List<String> getSortCode() {
 return sortCode;
 }
 public void setSortCode(List<String> sortCode) {
 this.sortCode = sortCode;
 }
 @Override
 public String toString() {
 return "{group:" + group + ", sortCode:" + sortCode + "}";
 }
}
import java.util.List;
public class Sort {
 private List<Message> messages;
 @Override
 public String toString() {
 return messages + "";
 }
 public List<Message> getMessages() {
 return messages;
 }
 public void setMessages(List<Message> messages) {
 this.messages = messages;
 }
}

And it seemed to work.