循环嵌套ArrayList以使用gson显示来自JSON的值

问：我的json有嵌套元素forms的值，正如你在下面看到的，我在数组中有来自服务器的值，而且里面有第二个数组。 现在我使用gson来解析这个值，每一件事都在起作用 – 直到"orderDetailList"但是当我尝试循环抛出“subItemPart”时，我无法检索subItemPart对象的值。

源代码：

在文件myFile.json中输入JSON字符串（使用JSONLintvalidation：有效的JSON）

 { "customerId": "CUST01", "orderId": "101010", "orderTotal": 99.99, "orderDetailList": [ { "lineId": "1", "itemNumber": "ABC", "quantity": 9, "price": 10.0, "subItemPart":[{"itemName":"RAM", "quantity": 5}, {"itemName":"LED", "quantity": 3}] }, { "lineId": "2", "itemNumber": "XYZ", "quantity": 1, "price": 9.99 , "subItemPart":[{"itemName":"RAM", "quantity": 5}, {"itemName":"LED", "quantity": 3}] } ] } 

用于将JSON字符串转换为Java对象的Java源代码

 package com.as400samplecode; import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import com.as400samplecode.util.OrderDetail; import com.as400samplecode.util.OrderHeader; import com.google.gson.Gson; public class ParseJSON { public static void main(String[] args) { String myJSONString = ""; BufferedReader bufferedReader = null; try { String sCurrentLine; bufferedReader = new BufferedReader(new FileReader("data/myFile.json")); while ((sCurrentLine = bufferedReader.readLine()) != null) { myJSONString = myJSONString + sCurrentLine; } } catch (IOException e) { e.printStackTrace(); } finally { try { if (bufferedReader != null){ bufferedReader.close(); } } catch (IOException ex) { ex.printStackTrace(); } } Gson gson = new Gson(); OrderHeader orderHeader = gson.fromJson(myJSONString, OrderHeader.class); System.out.println("Order Information --->"); System.out.println("Customer Id: " + orderHeader.getCustomerId()); System.out.println("Order Id: " + orderHeader.getOrderId()); System.out.println("Order Total: " + orderHeader.getOrderTotal()); ArrayList orderDetailList = orderHeader.getOrderDetailList(); for (int i=0; i"); OrderDetail orderDetail = orderDetailList.get(i); System.out.println("Line Id: " + orderDetail.getLineId()); System.out.println("Item Number: " + orderDetail.getItemNumber()); System.out.println("Quantity: " + orderDetail.getQuantity()); System.out.println("Price: " + orderDetail.getPrice()); **//HOW CAN I HERE LOOP AND DISPLAY VALUES OF SubOrderItem?** //I GET error when i do: System.out.println("SubItem: " +orderDetail.getSubOrderDetail.itemName); } } } 

OrderHeader对象的Java源代码

 package com.as400samplecode.util; import java.util.ArrayList; public class OrderHeader { String customerId = null; String orderId = null; Double orderTotal = null; ArrayList orderDetailList; public String getCustomerId() { return customerId; } public void setCustomerId(String customerId) { this.customerId = customerId; } public String getOrderId() { return orderId; } public void setOrderId(String orderId) { this.orderId = orderId; } public Double getOrderTotal() { return orderTotal; } public void setOrderTotal(Double orderTotal) { this.orderTotal = orderTotal; } public ArrayList getOrderDetailList() { return orderDetailList; } public void setOrderDetailList(ArrayList orderDetailList) { this.orderDetailList = orderDetailList; } } 

OrderDetail对象的Java源代码

 package com.as400samplecode.util; public class OrderDetail { String lineId = null; String itemNumber = null; int quantity = 0; Double price = null; ArrayList subItemPart; public String getLineId() { return lineId; } public void setLineId(String lineId) { this.lineId = lineId; } public String getItemNumber() { return itemNumber; } public void setItemNumber(String itemNumber) { this.itemNumber = itemNumber; } public int getQuantity() { return quantity; } public void setQuantity(int quantity) { this.quantity = quantity; } public Double getPrice() { return price; } public void setPrice(Double price) { this.price = price; } public ArrayList getSubOrderDetail() { return subItemPart; } public void setSubOrderDetail(ArrayList subItemPart) { this.subItemPart = subItemPart; } } 

//我的问题是如何获取此元素的值，因为它们是json嵌套数组的值， SubItemPart对象的Java源代码

 package com.as400samplecode.util; public class SubOrderDetail { String itemName = null; int quantity = 0; public String getLineId() { return itemName; } public void setLineId(String itemName) { this.itemName = itemName; } public int getItemNumber() { return quantity; } public void setItemNumber(int quantity) { this.quantity = quantity; } } 

谢谢。

Answer 1

好吧，首先你的class级名字有些混乱。 因为在您的OrderDetail类中，您有：

 ArrayList subItemPart; //... public ArrayList getSubOrderDetail() { return subItemPart; } public void setSubOrderDetail(ArrayList subItemPart) { this.subItemPart = subItemPart; } 

然后你的另一课是：

 public class SubOrderDetail { 

那么……你是否意识到同一个类有3个不同的名字（即SubOrderItemDetail ， SubItemDetail和SubOrderDetail ）？

---

也就是说，如果您使用名称解决了问题，那么您的代码就可以正常工作，而且只显示一个非常简单的问题。 要在a中显示子列表for您只需在具有注释行的位置添加此代码：

 ArrayList subOrderDetailList = orderDetail.getSubOrderDetail(); for (int j = 0; j < orderDetailList.size(); j++) { System.out.println("Sub Order Detail --->"); SubOrderItemDetail subOrderDetail = subOrderDetailList.get(j); System.out.println("Line Id: " + subOrderDetail.getLineId()); System.out.println("Item Number: " + subOrderDetail.getItemNumber()); } 

请注意，在我编写的代码中，我遵循您之前代码中的样式，但我更喜欢这种方式：

 for (SubOrderItemDetail soid : orderDetail.getSubOrderDetail()) { System.out.println("Line Id: " + soid.getLineId()); System.out.println("Item Number: " + soid.getItemNumber()); } 

您也可以在之前的版本中for此样式，您的代码将更加清晰……

Answer 2

在OrderDetail类而不是

  `ArrayList orderDetailList;` 

应该

ArrayList subItemPart;

和JSON一样。

并在SubOrderDetail类中删除

ArrayList subItemPart;

这应该可以解决问题。