DemoJackson

package beans;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;

public class DemoJackson {
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static void testDataBinding() {
        ObjectMapper om = new ObjectMapper();
        Map<String, Object> studentDataMap = new LinkedHashMap<String, Object>();

        Student stud = new Student();
        stud.setName("Dusko");
        stud.setAge(21);

        studentDataMap.put("student", stud);
        studentDataMap.put("faculty", "PMF");
        int[] marks = {9, 10, 10};
        studentDataMap.put("marks", marks);
        studentDataMap.put("verified", Boolean.FALSE);

        try {
            om.writeValue(new File("student1.json"), studentDataMap);
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            LinkedHashMap<Student, Object> studentDataMapRead = om.readValue(new File("student1.json"), LinkedHashMap.class);
            LinkedHashMap<String, Object> studRead = (LinkedHashMap) studentDataMapRead.get("student");
            System.out.println(studRead.get("name") + " " + studRead.get("age"));
            System.out.println(studentDataMapRead.get("faculty") + " " + studentDataMapRead.get("verified"));
            ArrayList<Integer> marksRead = (ArrayList<Integer>) studentDataMapRead.get("marks");
            for (int i = 0; i < marksRead.size(); i++)
                System.out.println(marksRead.get(i) + " ");
            System.out.println();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @SuppressWarnings("rawtypes")
    private static void testTreeMode() {
        ObjectMapper om = new ObjectMapper();
        String json = ("{\"student\": {\"name\": \"Dusko\", \"age\": 25}, \"faculty\":\"PMF\", \"marks\": [9, 10, 10], \"verified\": false}");
        JsonNode root;

        try {
            root = om.readTree(json);
            JsonNode student = root.path("student");
            String name = student.path("name").asText();
            int age = student.path("age").asInt();
            String faculty = root.path("faculty").asText();
            boolean verified = root.path("verified").asBoolean();
            JsonNode marks = root.path("marks");
            Iterator i = (Iterator) marks.elements();

            System.out.printf("%s %d %s %b\n", name, age, faculty, verified);

            while (i.hasNext())
                System.out.println(i.next());

        } catch (IOException e) {
            e.printStackTrace();
        }

        JsonNode rootWrite = om.createObjectNode();
        JsonNode marksNodeWrite = om.createArrayNode();
        ((ArrayNode) marksNodeWrite).add(10);
        ((ArrayNode) marksNodeWrite).add(10);
        ((ArrayNode) marksNodeWrite).add(10);

        JsonNode studNode = om.createObjectNode();
        ((ObjectNode) studNode).put("name", "Dusko");
        ((ObjectNode) studNode).put("age", 21);

        ((ObjectNode)rootWrite).set("student", studNode);
        ((ObjectNode)rootWrite).put("faculty", "PMF");
        ((ObjectNode)rootWrite).put("verified", Boolean.FALSE);
        ((ObjectNode)rootWrite).set("marks", marksNodeWrite);

        try {
            om.writeValue(new File("student2.json"), rootWrite);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void testStreamingMode() {
        JsonFactory factory = new JsonFactory();
        JsonGenerator generator;

        try {
            generator = factory.createGenerator(new File("student3.json"), JsonEncoding.UTF8);
            generator.writeStartObject();
            generator.writeStringField("name", "Dusko");
            generator.writeNumberField("age", 21);
            generator.writeStringField("faculty", "PMF");
            generator.writeBooleanField("verified", Boolean.FALSE);

            generator.writeFieldName("marks");
            generator.writeStartArray();
                generator.writeNumber(10);
                generator.writeNumber(10);
                generator.writeNumber(10);
            generator.writeEndArray();

            generator.writeEndObject();
            generator.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        JsonParser parser;
        try {
            parser = factory.createParser(new File("student3.json"));
            while (parser.nextToken() != JsonToken.END_OBJECT) {
                String fieldName = parser.getCurrentName();
                if ("name".equals(fieldName)) {
                    parser.nextToken();
                    System.out.println(parser.getText());
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
//      testDataBinding();
//      testTreeMode();
        testStreamingMode();
    }
}