CODEWITHSUNDEEP
jsonjackson
sreeraag
sreeraag

Reputation: 523

Recursively parsing a json file using Jackson Json parser

I'm trying to recursively parse a sample Json file that has many sets of complex elements. And the code that i'm trying is this : 

public class Jsonex {
    public static void main(String argv[]) {
        try {
            Jsonex jsonExample = new Jsonex();
           jsonExample.testJackson();
        } catch (Exception e){
            System.out.println("Exception " + e);
        }       
    }
    public static void testJackson() throws IOException {       
        JsonFactory factory = new JsonFactory();
       // System.out.println("hello");
        ObjectMapper mapper = new ObjectMapper(factory);
        File from = new File("D://albumList.txt");
        TypeReference<HashMap<String,Object>> typeRef = new TypeReference<HashMap<String,Object>>() {};
        HashMap<String,Object> o= mapper.readValue(from, typeRef);
       // System.out.println("" + o);
        Iterator it = o.entrySet().iterator();
       while (it.hasNext()) {

          Map.Entry pairs = (Map.Entry)it.next();
            System.out.println(pairs.getKey() + " = " + pairs.getValue());

           HashMap<String,Object> o1=mapper.readValue(pairs.getValue().toString(),typeRef);
          System.out.println("hey"+o1);
           Iterator it1 = o1.entrySet().iterator();
           while (it1.hasNext()) {
                Map.Entry pairs1 = (Map.Entry)it.next();
                System.out.println(pairs1.getKey() + " = " + pairs1.getValue());
            it1.remove(); // avoids a ConcurrentModificat



    }   
    }
}}

and i get this exception :

Exception org.codehaus.jackson.JsonParseException: Unexpected character ('i' (code 105)): was expecting double-quote to start field name at [Source: java.io.StringReader@2de7753a; line: 1, column: 3]

Actually what im trying to do is, parse the file and get list of name object pairs, and take the object which inturn has name-object pairs. - but the problem is that the parser is expecting "" before strings !

Upvotes: 4

Views: 11228

Answers (2)

Diego Palomar
Diego Palomar

Reputation: 7061

Just a comment. As you know there are 3 major processing modes that Jackson supports (Data Binding, Streaming API and Tree Model). You need to take into account that if you decide to use the Tree Model, acording to the official docs, the memory usage is proportional to content mapped (similar to data binding), so tree models can NOT be used with huge Json content, unless mapping is done chunk at a time. This is the same problem that data binding encounters; and sometimes the solution is to use Stream-of-Events instead.

Upvotes: 4

nutlike
nutlike

Reputation: 4975

Instead of parsing everything by yourself you should consider to use Jacksons built-in tree model feature (http://wiki.fasterxml.com/JacksonTreeModel):

ObjectMapper mapper = new ObjectMapper(factory);
File from = new File("D://albumList.txt");
JsonNode rootNode = mapper.readTree(from);  

Iterator<Map.Entry<String,JsonNode>> fields = rootNode.fields();
while (fields.hasNext()) {

    Map.Entry<String,JsonNode> field = fields.next();
    System.out.println(field.getKey() + " = " + field.getValue());
    …

}

This should be more convenient in the long run. Have a look at the API at http://fasterxml.github.com/jackson-databind/javadoc/2.1.0/com/fasterxml/jackson/databind/JsonNode.html.

Upvotes: 5

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