Error converting JSON string to map in Java using Jackson
17,009
Solution 1
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>'}";
Solution 2
Right: you're asking Jackson to map a JSON Array into an object; there is no obvious way to do that. So, tofarr's answer is correct.
But if you wanted a List or an array, you could achieved it easily by:
List<?> list = mapper.readValue(json, List.class);
Or with full type reference; optional in this case because you just want Lists, Maps and Strings.
Author by
Laphroaig
Updated on June 15, 2022Comments
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Laphroaig about 2 years
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?