Jackson樹模型

樹模型準備JSON文件的內(nèi)存樹表示。 ObjectMapper構建JsonNode節(jié)點樹。這是最靈活的方法。它類似于DOM解析器的XML。

從JSON創(chuàng)建樹

ObjectMapper提供一個指針樹的根節(jié)點在讀取JSON之后。根節(jié)點可用于遍歷完全樹?？紤]下面的代碼片段獲得提供JSON字符串的根節(jié)點。

//Create an ObjectMapper instance
ObjectMapper mapper = new ObjectMapper();	
String jsonString = "{\"name\":\"Mahesh Kumar\", \"age\":21,\"verified\":false,\"marks\": [100,90,85]}";
//create tree from JSON
JsonNode rootNode = mapper.readTree(jsonString);

遍歷樹模型

使用相對路徑來根節(jié)點在遍歷樹，并處理該數(shù)據(jù)得到的每個節(jié)點?？紤]下面的代碼片段遍歷提供的根節(jié)點的樹。

JsonNode nameNode = rootNode.path("name");
System.out.println("Name: "+ nameNode.getTextValue());
 
JsonNode marksNode = rootNode.path("marks");
Iterator iterator = marksNode.getElements();

示例

創(chuàng)建一個名為JacksonTester在Java類文件目錄 C:\>Jackson_WORKSPACE.

File: JacksonTester.java

import java.io.IOException;
import java.util.Iterator;

import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

public class JacksonTester {
   public static void main(String args[]){
      JacksonTester tester = new JacksonTester();
      try {
         ObjectMapper mapper = new ObjectMapper();
         String jsonString = "{\"name\":\"Mahesh Kumar\", \"age\":21,\"verified\":false,\"marks\": [100,90,85]}";
         JsonNode rootNode = mapper.readTree(jsonString);

         JsonNode nameNode = rootNode.path("name");
         System.out.println("Name: "+ nameNode.getTextValue());

         JsonNode ageNode = rootNode.path("age");
         System.out.println("Age: " + ageNode.getIntValue());

         JsonNode verifiedNode = rootNode.path("verified");
         System.out.println("Verified: " + (verifiedNode.getBooleanValue() ? "Yes":"No"));

         JsonNode marksNode = rootNode.path("marks");
         Iterator<JsonNode> iterator = marksNode.getElements();
         System.out.print("Marks: [ ");
         while (iterator.hasNext()) {
            JsonNode marks = iterator.next();
            System.out.print(marks.getIntValue() + " "); 
         }
         System.out.println("]");
      } catch (JsonParseException e) {
         e.printStackTrace