No content to map due to end-of-input

The fix

Check the body before you read it, as in the fixed code: json.isBlank() ? null : mapper.readValue(json, Order.class). Then find out why it was empty. That is usually the real bug.

public class Order {
  public long id;
  public String status;
}

Order order = mapper.readValue(json, Order.class);

public class Order {
  public long id;
  public String status;
}

Order order = json.isBlank() ? null : mapper.readValue(json, Order.class);

How the message appears

Jackson 2, then Jackson 3, then Spring (the same on 6.2 and 7.0). Jackson 2 gives a line but no column, and Jackson 3 gives an unknown byte offset.

What causes it

1. 1

   The body is empty

   The example is an empty string. There is nothing to read, so Jackson 2 and 3 both say No content to map due to end-of-input.

2. 2

   An empty response or request

   Whatever made the body empty, this is the message. Look for a response with no body, or a call that failed before it returned anything. Spring's Jackson converter prints it as JSON parse error: No content to map due to end-of-input. Whether an empty request ever gets as far as the converter depends on what runs before it in your app, which was not tested here. Other Spring messages are on the Spring page.

3. 3

   The body was already read

   A stream can only be read once. If something read the body before Jackson, Jackson gets nothing. Look for a logging filter or a second readValue on the same stream.

Worth knowing