树模型准备JSON文档的内存树表示. ObjectMapper构建JsonNode节点的树.这是最灵活的方法.它类似于XML的DOM解析器.
ObjectMapper在读取JSON后提供指向树的根节点的指针.根节点可用于遍历整个树.请考虑以下代码片段以获取所提供的JSON字符串的根节点.
//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);
在遍历树并处理数据时,使用相对路径获取每个节点.考虑以下代码片段遍历提供根节点的树.
JsonNode nameNode = rootNode.path("name"); System.out.println("Name: "+ nameNode.textValue()); JsonNode marksNode = rootNode.path("marks"); Iterator<JsonNode> iterator = marksNode.elements();
在 C:\> Jackson_WORKSPACE .
文件:JacksonTester.java
import java.io.IOException; import java.util.Iterator; import com.fasterxml.jackson.core.JsonParseException; import com.fasterxml.jackson.databind.JsonMappingException; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; public class JacksonTester { public static void main(String args[]){ 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.textValue()); JsonNode ageNode = rootNode.path("age"); System.out.println("Age: " + ageNode.intValue()); JsonNode verifiedNode = rootNode.path("verified"); System.out.println("Verified: " + (verifiedNode.booleanValue() ? "Yes":"No")); JsonNode marksNode = rootNode.path("marks"); Iterator<JsonNode> iterator = marksNode.elements(); System.out.print("Marks: [ "); while (iterator.hasNext()) { JsonNode marks = iterator.next(); System.out.print(marks.intValue() + " "); } System.out.println("]"); } catch (JsonParseException e) { e.printStackTrace(); } catch (JsonMappingException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }
验证结果
使用 javac 编译器编译类,如下所示:
C:\ _Jackson_WORKSPACE> javac JacksonTester.java
现在运行jacksonTester查看结果:
C:\ Jackson_WORKSPACE> java JacksonTester
验证输出
Name: Mahesh Kumar Age: 21 Verified: No Marks: [ 100 90 85 ]
Tree to JSON
Tree to Java Objects