Question

对于以下JSON，我想将地址元素打印到控制台

[
        {
                "firstName": "Lakshay",
        "lastName": "Sharma",
        "age": 35,
        "emailAddress": "Lakshay@Gmail.com",
        "address": {
            "streetAddress": "Shalimar Bagh",
            "city": "Delhi",
            "postCode": "110088",
            "state": "Delhi",
            "country": "India",
            "county": "Delhi"
        },
        "phoneNumber": {
            "home": "012345678",
            "mob": "0987654321"
        }
    },
    {
        "firstName": "Virender",
        "lastName": "Singh",
        "age": 35,
        "emailAddress": "Virender@Gmail.com",
        "address": {
            "streetAddress": "Palam Vihar",
            "city": "Gurgaon",
            "postCode": "122345",
            "state": "Haryana",
            "country": "India",
            "county": "Delhi"
        },
        "phoneNumber": {
            "home": "012345678",
            "mob": "0987654321"
        }
    }
]

这是我的Java类，我存储了JSON键的所有数据类型，并创建了3个类.Class CustomerDataType也包含PhoneNumber和Address类。

package com.practice.SeleniumWebDriver;

public class CustomerDataTypes {

          public String firstName;
          public String lastName;
          public int age;
          public String emailAddress;
          public Address address;
          public PhoneNumber phoneNumber;   

          public static class Address {
              public String streetAddress;
              public String city;
              public String postCode;
              public String state;
              public String country;
              public String county;
          }

          public class PhoneNumber {
              public String home;
              public String mob;
          }
    }

在我的Main类中，我编写了下面的代码来访问JSON的所有元素，但在获取Address类（它是CustomerDataTypes的内部类）时遇到问题

package com.practice.SeleniumWebDriver;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Arrays;
import java.util.List;

import com.google.gson.Gson;
import com.google.gson.stream.JsonReader;
import com.practice.SeleniumWebDriver.CustomerDataTypes.Address;

public class ReadJsonData {
    private static List<CustomerDataTypes> customerList;
    public static List<CustomerDataTypes.Address> CustomerAddress;
    //private static List<CustomerDataTypes.PhoneNumber> CustomerPhoneNumber;

public static String CustomerFilePath="D:\\eclipse-workspace\\SeleniumWebDriver\\src\\test\\java\\testDataTypes\\CustomerData.json";


    public static void  main(String args[]) throws FileNotFoundException 
    {

    customerList=separator();
    getCustomerByName("firstName");
    CustomerAddress=SeparatorForAddress();
    getCustomerAddress("streetAddress");

    }

    public static List<CustomerDataTypes> separator() throws FileNotFoundException
    {
    Gson gson=new Gson();
    JsonReader reader=new JsonReader(new FileReader(CustomerFilePath));
CustomerDataTypes[] data=gson.fromJson(reader, CustomerDataTypes[].class);
System.out.println(Arrays.asList(data));
return Arrays.asList(data);


}
    public final static CustomerDataTypes getCustomerByName(String customerName){
        for(CustomerDataTypes customer : customerList) {

            if(customer.firstName.equalsIgnoreCase(customerName))

                System.out.println("");
            System.out.println(customer.firstName);
            System.out.println(customer.lastName);
            //System.out.println(customer.address);

                return customer;
        }
        return null;
    }
    public static List<Address> SeparatorForAddress() throws FileNotFoundException
    {
    Gson gson=new Gson();
    JsonReader reader=new JsonReader(new FileReader(CustomerFilePath));
Address[] data=gson.fromJson(reader, Address[].class);
System.out.println(Arrays.asList(data));
return Arrays.asList(data);



}
    public final static CustomerDataTypes.Address getCustomerAddress(String adr)
    {
        for(CustomerDataTypes.Address address : CustomerAddress )
        {
            System.out.println(address.streetAddress);
            System.out.println(CustomerAddress);
            if(address.streetAddress.equals(adr))

                System.out.println("Hello");
                System.out.println(address.streetAddress);
            System.out.println(address.country);
            System.out.println(address.postCode);
            return address;
        }
        return null;
    }
    }

在上面的Main Class中，getCustomerAddress（），S.O.P（address.streetAddress）抛出空值。

以下是控制台上的输出：

[com.practice.SeleniumWebDriver.CustomerDataTypes@17579e0f, com.practice.SeleniumWebDriver.CustomerDataTypes@4d41cee]
Lakshay
Sharma
[com.practice.SeleniumWebDriver.CustomerDataTypes$Address@3712b94, com.practice.SeleniumWebDriver.CustomerDataTypes$Address@2833cc44]
null
java.lang.NullPointerException
    at com.practice.SeleniumWebDriver.ReadJsonData.getCustomerAddress(ReadJsonData.java:72)
    at com.practice.SeleniumWebDriver.ReadJsonData.main(ReadJsonData.java:25)

你能帮忙搞清楚吗？

Answer 1

如果我修改了getCustomerByName（）方法，我可以得到所有类的结果。

public final static CustomerDataTypes getCustomerByName(String customerName){

        System.out.println(customerList.size());

            for(int i=0;i<customerList.size();i++)
            {
                System.out.println("The value of i is" +i);
                System.out.println(customerList.get(i).firstName);
                System.out.println(customerList.get(i).lastName);
                System.out.println(customerList.get(i).emailAddress);
                System.out.println(customerList.get(i).address.city);
                System.out.println(customerList.get(i).phoneNumber.mob);


            }

        return null;
    }

Answer 2

由于您正在从NullPointerException方法返回null

}，您将获得getCustomerByName()

public final static CustomerDataTypes getCustomerByName(String customerName){

    System.out.println(customerList.size());

        for(int i=0;i<customerList.size();i++) {
            System.out.println("The value of i is" +i);
            System.out.println(customerList.get(i).firstName);
            System.out.println(customerList.get(i).lastName);
            System.out.println(customerList.get(i).emailAddress);
            System.out.println(customerList.get(i).address.city);
            System.out.println(customerList.get(i).phoneNumber.mob);
        }

    return null;  // root cause for the Exception
}

进行如下修改，

public final static CustomerDataTypes getCustomerByName(String customerName){

    System.out.println(customerList.size());

        for(int i = 0; i < customerList.size(); i++) {
            System.out.println("The value of i is" +i);
            System.out.println(customerList.get(i).firstName);
            System.out.println(customerList.get(i).lastName);
            System.out.println(customerList.get(i).emailAddress);
            System.out.println(customerList.get(i).address.city);
            System.out.println(customerList.get(i).phoneNumber.mob);

            // changes to be made
            CustomerDataTypes custData = customerList.get(i);

            if (customerName.equalsIgnoreCase(custData.firstName)) {
                return custData;
            }
        }

    return null;
}

如果您从null方法返回getCustomerByName()，如果给定名称不匹配，则应在使用该对象之前检查空安全性。

CustomerDataTypes data = getCustomerByName("Virender");

if (data != null) {
  // code
}

请注意，我将实际用户名（Virender）作为参数传递给getCustomerByName()方法而不是您在代码中使用的JSON密钥。

同样适用于getCustomerByAddress()方法。根据您的要求进行更改。

通过GSON获取作为对象内对象的JSON值的问题

2 个答案: