jackson-data-binding

A simple Java application demonstrating how to map JSON to POJO using the Jackson library.

Technologies Used

• IDE Intellij IDEA
• Java Version JDK 1.8 (Java 8)
• Maven Dependencies:
  • jackson-core (v2.16.1)
  • jackson-databind (v2.16.1)

Errors and Troubleshooting

If you are testing this code and remove some parts, you might run into this error:

Exception in thread "main" com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of Student (no Creators, like default constructor, exist): cannot deserialize from Object value no delegate- or property-based Creator ....

Why it happens: Jackson requires a blank, default constructor (such as public Student() { }) to build the empty object before it can inject the JSON data.

Same Solution for similar case: If you're interested, you can read this discussion: Stackoverflow Discussion

Concepts Demonstrated

• Basic Data Binding: Converting flat JSON to Java Objects.
• Nested Objects: Mapping JSON objects within objects to separate custom POJOs (such as mapping a director JSON object to a Director.java class).
• Collections: Automatically mapping JSON arrays to Java List<String>.
• Jackson Annotations:
  • @JsonProperty: Resolving naming convention mismatches between JSON (snake_case or capitalized fields) and Java (camelCase).
  • @JsonIgnore: Securing sensitive data by ignoring specific fields during serialization (hiding internal variables from the final JSON output).