如何用Java中的Jackson对象模型映射JSON数据？
ObjectMapper类提供用于在Java对象和匹配的JSON构造之间进行转换的功能。 我们可以使用树状数据结构（将整个JSON内容读取并存储在内存中）来实现将对象模型表示的JSON数据映射到特定的Java对象。 第一步，将JSON数据读取到JsonNode对象中，然后通过调用ObjectMapper类的treeToValue()方法将其映射到另一个实例。
语法
public <T> T treeToValue(TreeNode n, Class<T> valueType) throws JsonProcessingException
示例
import java.io.*;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;
public class JsonTreeModelDemo {
public static void main(String[] args) throws JsonProcessingException, IOException {
String jsonString = "{\"id\":\"102\", \"name\":\"Raja Ramesh\", \"address\":[{\"area\":\"Madhapur\", \"city\":\"Hyderabad\"}]}";
ObjectMapper objectMapper = new ObjectMapper();
JsonNode jsonNode = objectMapper.readTree(jsonString);
User user = objectMapper.treeToValue(jsonNode, User.class);
System.out.println(user);
}
}
// User class
class User {
private int id;
private String name;
private Address[] address;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Address[] getAddress() {
return address;
}
public void setAddress(Address[] address) {
this.address = address;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("{");
sb.append(id).append(",");
sb.append(name).append(",");
for(Address address1 : address) {
sb.append(address1).append(",");
}
sb.append("}");
return sb.toString();
}
}
// Address class
class Address {
private String area;
private String city;
public String getArea() {
return area;
}
public void setArea(String area) {
this.area = area;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("{");
sb.append(area).append(",");
sb.append(city);
sb.append("}");
return sb.toString();
}
}输出结果
{102,Raja Ramesh,{Madhapur,Hyderabad},}