Hey there! Let's break down why you're hitting this error and how to fix it properly.

Why the Error Happens #

That UnrecognizedPropertyException is telling you your JSON structure doesn't match the Inventory case class you defined. Here's the mismatch:

• Your JSON is a top-level object with three keys: Rice, Pulses, Wheats — each maps to an array of items with name and price.
• But your Inventory class only has name and price fields. Jackson is trying to shove the entire JSON (with those Rice/Pulses/Wheats keys) into an Inventory instance, which has no place for those keys — hence the error.

How to Fix It #

We need to align your Scala classes with the actual structure of your JSON. Here are two solid approaches:

Approach 1: Define Case Classes That Match the JSON Structure #

Let's create two layers of case classes: one for individual items, and one for the top-level inventory structure.

// Case class for a single item (matches the objects inside each array)
case class Item(name: String, price: Int) // Note: price is an Int, not String (your JSON uses numbers!)

// Case class for the entire inventory (matches the top-level JSON object)
case class InventoryData(Rice: List[Item], Pulses: List[Item], Wheats: List[Item])

object InventoryDataManagement {
  def main(args: Array[String]): Unit = {
    val mapper = JsonMapper.builder()
      .addModule(DefaultScalaModule)
      .build()
    val src = new File("src/main/json/inventary.json")
    
    // Map the JSON to our InventoryData class instead of Inventory
    val inventory = mapper.readValue(src, classOf[InventoryData])
    
    // Example: Print all rice items
    println("Rice Inventory:")
    inventory.Rice.foreach(item => println(s"${item.name} - ₹${item.price}"))
    
    // Print pulses too!
    println("\nPulses Inventory:")
    inventory.Pulses.foreach(item => println(s"${item.name} - ₹${item.price}"))
  }
}

Approach 2: Use a Map for Flexible Category Handling #

If you might add more categories later (like Spices or Oils) and don't want to update your case class every time, map the JSON directly to a Map[String, List[Item]]:

case class Item(name: String, price: Int)

object InventoryDataManagement {
  def main(args: Array[String]): Unit = {
    val mapper = JsonMapper.builder()
      .addModule(DefaultScalaModule)
      .build()
    val src = new File("src/main/json/inventary.json")
    
    // Map the JSON to a Map where keys are category names, values are item lists
    val inventoryMap = mapper.readValue(src, classOf[Map[String, List[Item]]])
    
    // Loop through all categories and their items
    inventoryMap.foreach { case (category, items) =>
      println(s"\n$category:")
      items.foreach(item => println(s"  • ${item.name}: ₹${item.price}"))
    }
  }
}

Quick Extra Tips #

• Fix the Price Type: Your original Inventory class had price as a String, but your JSON uses numeric values. Changing it to Int (or Double if you have decimals) avoids unnecessary type conversions and errors.
• Ignore Unknown Fields (Optional): If you ever have JSON with extra fields you don't care about, you can tell Jackson to ignore them to avoid similar errors:

  val mapper = JsonMapper.builder()
    .addModule(DefaultScalaModule)
    .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
    .build()
  

内容的提问来源于stack exchange，提问作者Piyush Jiwane