如何遍历多个JsonObject？特定结构JSON遍历仅获最后一项问题

Hey Joshua, I’ve run into this exact issue before—let’s break down why you’re only seeing the last item and fix it right away!

The Most Common Culprit: Overwriting a Single Variable #

Chances are your code looks something like this, where you’re reusing the same JsonObject variable in each loop iteration, overwriting its content every time:

// ❌ Wrong approach: Overwriting the same object each loop
JsonObject singleResult = new JsonObject();
JsonArray jsonArray = yourOriginalJson.getAsJsonArray();

for (JsonElement element : jsonArray) {
    JsonObject currentObj = element.getAsJsonObject();
    // This replaces the existing "data" entry every time
    singleResult.add("data", currentObj.get("targetField"));
}

// singleResult will only hold the last iteration's data

The Fix: Collect Objects in a Collection or JsonArray #

Instead of overwriting one object, you need to collect each traversed JsonObject into a list or a new JsonArray. Here are two straightforward solutions:

Solution 1: Store All Objects in a List<JsonObject>

This is great if you need to work with the objects in your Java code later:

// ✅ Correct approach: Collect into a List
List<JsonObject> allJsonObjects = new ArrayList<>();
JsonArray sourceArray = yourOriginalJson.getAsJsonArray();

for (JsonElement element : sourceArray) {
    // Always check if the element is a JsonObject to avoid errors
    if (element.isJsonObject()) {
        JsonObject obj = element.getAsJsonObject();
        allJsonObjects.add(obj); // Add each object to the list instead of overwriting
    }
}

// Now you can iterate through the list to access all items
for (JsonObject obj : allJsonObjects) {
    String desiredValue = obj.get("yourKey").getAsString();
    System.out.println("Item: " + desiredValue);
}

Solution 2: Build a New JsonArray for JSON Output

If you need to return or save the result as a JSON array, construct a new JsonArray and add each processed object to it:

// ✅ Correct approach: Build a result JsonArray
JsonArray resultArray = new JsonArray();
JsonArray sourceArray = yourOriginalJson.getAsJsonArray();

for (JsonElement element : sourceArray) {
    if (element.isJsonObject()) {
        JsonObject currentObj = element.getAsJsonObject();
        // Optional: Process the object (e.g., extract specific fields)
        JsonObject processedObj = new JsonObject();
        processedObj.addProperty("id", currentObj.get("id").getAsInt());
        processedObj.addProperty("name", currentObj.get("name").getAsString());
        
        resultArray.add(processedObj); // Append to the array, no overwriting
    }
}

// resultArray now contains all your items as valid JSON
System.out.println(resultArray.toString());

Key Takeaway #

The root issue is that you were modifying a single JsonObject instance through each loop iteration—each pass replaced the previous data. By collecting each object into a list or array, you preserve every item you traverse.

Quick pro tip: Always add a check with element.isJsonObject() before casting to avoid ClassCastException if your JSON array has mixed element types!

内容的提问来源于stack exchange，提问作者Joshua