Java提取JSON中industryIdentifiers的identifier值避免丢数求助

I see exactly what's going wrong here—your code has two critical mistakes that are causing digit loss and incorrect parsing:

1. You’re treating items as a JSONObject, but it’s actually a JSONArray (look at the square brackets [] around it in your response).
2. You’re calling getString(0) on the industryIdentifiers array, but each element in that array is a JSONObject (not a raw string), so you need to access the identifier field inside each object.

Correct Approach Using the org.json Library #

Here’s the fixed code that properly extracts all identifiers without losing any digits (including leading zeros in ISBN_10):

import org.json.JSONArray;
import org.json.JSONObject;

public class IsbnExtractor {
    public static void main(String[] args) {
        String jsonResponse = "{ \"items\": [ { \"volumeInfo\": { \"industryIdentifiers\": [ { \"type\": \"ISBN_10\", \"identifier\": \"0080509576\" }, { \"type\": \"ISBN_13\", \"identifier\": \"9780080509570\" } ] } } ] }";
        
        // Parse the root JSON object
        JSONObject rootObj = new JSONObject(jsonResponse);
        
        // Get the items array (since items is an array, not a single object)
        JSONArray itemsArray = rootObj.getJSONArray("items");
        
        // Grab the first item in the array (adjust index if there are multiple items)
        JSONObject firstBookItem = itemsArray.getJSONObject(0);
        
        // Access the volumeInfo object
        JSONObject volumeInfo = firstBookItem.getJSONObject("volumeInfo");
        
        // Get the industryIdentifiers array
        JSONArray identifiersArray = volumeInfo.getJSONArray("industryIdentifiers");
        
        // Iterate through each identifier object to extract the value
        for (int i = 0; i < identifiersArray.length(); i++) {
            JSONObject identifierObj = identifiersArray.getJSONObject(i);
            String isbnType = identifierObj.getString("type");
            String isbnNumber = identifierObj.getString("identifier");
            System.out.println(isbnType + ": " + isbnNumber);
        }
    }
}

Why This Works #

• Proper array handling: We use getJSONArray("items") instead of getJSONObject("items") to correctly access the list of book items.
• String retrieval: Using getString("identifier") ensures we pull the exact string value from each object, avoiding any conversion to numeric types that would drop leading zeros or truncate digits.

Alternative: Using Jackson Library (Object Mapping) #

If you prefer a more type-safe approach with Jackson (a popular JSON processing library), here’s how to do it:

First, define simple POJO classes to map the JSON structure:

import com.fasterxml.jackson.annotation.JsonProperty;
import java.util.List;

public class BookResponse {
    @JsonProperty("items")
    private List<BookItem> items;

    // Getters and setters
    public List<BookItem> getItems() { return items; }
    public void setItems(List<BookItem> items) { this.items = items; }
}

class BookItem {
    @JsonProperty("volumeInfo")
    private VolumeInfo volumeInfo;

    // Getters and setters
    public VolumeInfo getVolumeInfo() { return volumeInfo; }
    public void setVolumeInfo(VolumeInfo volumeInfo) { this.volumeInfo = volumeInfo; }
}

class VolumeInfo {
    @JsonProperty("industryIdentifiers")
    private List<IndustryIdentifier> industryIdentifiers;

    // Getters and setters
    public List<IndustryIdentifier> getIndustryIdentifiers() { return industryIdentifiers; }
    public void setIndustryIdentifiers(List<IndustryIdentifier> industryIdentifiers) { this.industryIdentifiers = industryIdentifiers; }
}

class IndustryIdentifier {
    @JsonProperty("type")
    private String type;
    @JsonProperty("identifier")
    private String identifier;

    // Getters and setters
    public String getType() { return type; }
    public void setType(String type) { this.type = type; }
    public String getIdentifier() { return identifier; }
    public void setIdentifier(String identifier) { this.identifier = identifier; }
}

Then parse and extract the identifiers:

import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonIsbnExtractor {
    public static void main(String[] args) throws Exception {
        String jsonResponse = "{ \"items\": [ { \"volumeInfo\": { \"industryIdentifiers\": [ { \"type\": \"ISBN_10\", \"identifier\": \"0080509576\" }, { \"type\": \"ISBN_13\", \"identifier\": \"9780080509570\" } ] } } ] }";
        
        ObjectMapper objectMapper = new ObjectMapper();
        BookResponse response = objectMapper.readValue(jsonResponse, BookResponse.class);
        
        // Extract identifiers from the first book item
        List<IndustryIdentifier> identifiers = response.getItems().get(0).getVolumeInfo().getIndustryIdentifiers();
        for (IndustryIdentifier id : identifiers) {
            System.out.println(id.getType() + ": " + id.getIdentifier());
        }
    }
}

This approach maps JSON directly to Java objects, making your code more readable and less error-prone than manual parsing.

内容的提问来源于stack exchange，提问作者Sid