Laphroaig Laphroaig - 6 months ago 26
JSON Question

Error converting JSON string to map in Java using Jackson

I have this little piece of code, and I'm trying to convert a JSON string to a map.

String json = "[{'code':':)','img':'<img src=/faccine/sorriso.gif>'}]";
ObjectMapper mapper = new ObjectMapper();
Map<String,String> userData = mapper.readValue(json,new TypeReference<HashMap<String,String>>() { });


But it returns the following error:

org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.util.HashMap out of START_ARRAY token
at [Source: java.io.StringReader@1b1756a4; line: 1, column: 1]
at org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:163)
at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:198)
at org.codehaus.jackson.map.deser.MapDeserializer.deserialize(MapDeserializer.java:151)
at org.codehaus.jackson.map.deser.MapDeserializer.deserialize(MapDeserializer.java:25)
at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2131)
at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1402)
at CodeSnippet_19.run(CodeSnippet_19.java:13)
at org.eclipse.jdt.internal.debug.ui.snippeteditor.ScrapbookMain1.eval(ScrapbookMain1.java:20)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.jdt.internal.debug.ui.snippeteditor.ScrapbookMain.evalLoop(ScrapbookMain.java:54)
at org.eclipse.jdt.internal.debug.ui.snippeteditor.ScrapbookMain.main(ScrapbookMain.java:35)


What am I doing wrong?

Answer

From what I remember Jackson is used to convert json to java classes - it is probably expecting the first object is reads to be a map, like

String json = "{'code':':)','img':'<img src=/faccine/sorriso.gif>'}";