JSON Validation - potatoscript/json GitHub Wiki

✅ JSON Validation in Java: Ensure Your JSON is Correct! 🎯

Welcome to JSON Validation in Java – where we ensure that your JSON data is structured perfectly and error-free! 🎉🕵️‍♂️

🎯 What is JSON Validation?

JSON Validation is the process of verifying that a JSON document:

✅ Follows correct syntax.
✅ Contains valid data types.
✅ Adheres to a defined schema (optional but recommended for complex data structures).

🔥 1. Why Validate JSON?

JSON data exchanged between systems can sometimes be:

❌ Malformed (missing brackets, commas).
❌ Containing unexpected or invalid values.
❌ Missing required keys.

🎁 Common Errors:

{"name": "Lucy", "age": 26, } ➡️ ❌ Trailing comma.
{"name": "Lucy", "age": "twenty-six"} ➡️ ❌ Incorrect data type.

🧩 2. JSON Validation Methods in Java

There are multiple ways to validate JSON in Java:

⚡️ a) Basic Syntax Validation

You can validate basic JSON syntax using ObjectMapper from the Jackson library.

📚 Add Jackson to Your Project

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.15.0</version>
</dependency>

🎯 Example: Basic Syntax Validation with Jackson

import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonValidationExample {
    public static void main(String[] args) {
        String json = "{\"name\":\"Lucy Berry\",\"age\":26}";
        ObjectMapper mapper = new ObjectMapper();

        try {
            // Basic validation: Parse JSON to check syntax
            mapper.readTree(json);
            System.out.println("✅ JSON is valid!");
        } catch (Exception e) {
            System.out.println("❌ Invalid JSON: " + e.getMessage());
        }
    }
}

✅ Explanation:

readTree() parses the JSON.
If the JSON is invalid, an exception is thrown.

📌 b) JSON Schema Validation

To ensure JSON follows a defined schema, use the everit-org/json-schema library.

📚 Add JSON Schema Validator to Your Project

<dependency>
    <groupId>org.everit.json</groupId>
    <artifactId>org.everit.json.schema</artifactId>
    <version>1.14.3</version>
</dependency>

🎯 3. JSON Schema Basics

What is a JSON Schema?

📚 Defines the structure, data types, and constraints of a JSON document.
✅ Ensures that the JSON follows a predefined format.

📄 Sample JSON Schema:

{
  "type": "object",
  "properties": {
    "name": { "type": "string" },
    "age": { "type": "integer" },
    "email": { "type": "string", "format": "email" }
  },
  "required": ["name", "age"]
}

🎯 4. Validating JSON Against Schema in Java

🔥 Step 1: Create a JSON Schema File

Save the schema in user_schema.json:

{
  "type": "object",
  "properties": {
    "name": { "type": "string" },
    "age": { "type": "integer" },
    "email": { "type": "string", "format": "email" }
  },
  "required": ["name", "age"]
}

🔥 Step 2: Validate JSON Using Everit Library

import org.everit.json.schema.Schema;
import org.everit.json.schema.loader.SchemaLoader;
import org.json.JSONObject;
import org.json.JSONTokener;
import java.io.FileInputStream;

public class JsonSchemaValidationExample {
    public static void main(String[] args) {
        try {
            // Load JSON Schema
            FileInputStream schemaStream = new FileInputStream("user_schema.json");
            JSONObject jsonSchema = new JSONObject(new JSONTokener(schemaStream));

            // Load JSON Data
            String jsonData = """
                {
                    "name": "Lucy Berry",
                    "age": 26,
                    "email": "[email protected]"
                }
                """;
            JSONObject jsonObject = new JSONObject(jsonData);

            // Validate JSON
            Schema schema = SchemaLoader.load(jsonSchema);
            schema.validate(jsonObject);

            System.out.println("✅ JSON is valid against the schema!");
        } catch (Exception e) {
            System.out.println("❌ JSON validation failed: " + e.getMessage());
        }
    }
}

✅ Explanation:

SchemaLoader.load() loads the schema from the file.
schema.validate() checks JSON against the schema.

🎨 5. Custom JSON Validation with Jackson Annotations

If you prefer to use annotations to validate JSON properties, you can annotate Java classes.

🎯 Example: Using Jackson Annotations

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;
import javax.validation.constraints.*;

class User {
    @JsonProperty("name")
    @NotNull(message = "Name is required")
    private String name;

    @JsonProperty("age")
    @Min(value = 18, message = "Age must be 18 or above")
    private int age;

    @JsonProperty("email")
    @Email(message = "Invalid email format")
    private String email;

    // Getters and Setters
    public String getName() { return name; }
    public int getAge() { return age; }
    public String getEmail() { return email; }
}

public class AnnotationValidationExample {
    public static void main(String[] args) {
        String json = """
            {
                "name": "Lucy Berry",
                "age": 16,
                "email": "lucy.berry@invalid"
            }
            """;

        ObjectMapper mapper = new ObjectMapper();
        try {
            User user = mapper.readValue(json, User.class);
            System.out.println("✅ Valid JSON!");
        } catch (Exception e) {
            System.out.println("❌ JSON validation failed: " + e.getMessage());
        }
    }
}

✅ Explanation:

Use @NotNull, @Min, and @Email to validate fields.
Invalid data triggers validation errors.

🕵️‍♂️ 6. Validating Nested JSON in Java

When dealing with nested JSON, make sure the structure is properly validated.

🎯 Example: Nested JSON Validation

import com.fasterxml.jackson.databind.ObjectMapper;
import org.everit.json.schema.Schema;
import org.everit.json.schema.loader.SchemaLoader;
import org.json.JSONObject;
import org.json.JSONTokener;
import java.io.FileInputStream;

public class NestedJsonValidationExample {
    public static void main(String[] args) {
        try {
            // Load Nested JSON Schema
            FileInputStream schemaStream = new FileInputStream("nested_schema.json");
            JSONObject jsonSchema = new JSONObject(new JSONTokener(schemaStream));

            // Load Nested JSON Data
            String nestedJsonData = """
                {
                    "user": {
                        "name": "Lucy Berry",
                        "age": 26,
                        "address": {
                            "city": "Fukuoka",
                            "postal_code": "810-0011"
                        }
                    }
                }
                """;
            JSONObject jsonObject = new JSONObject(nestedJsonData);

            // Validate Nested JSON
            Schema schema = SchemaLoader.load(jsonSchema);
            schema.validate(jsonObject);

            System.out.println("✅ Nested JSON is valid!");
        } catch (Exception e) {
            System.out.println("❌ Nested JSON validation failed: " + e.getMessage());
        }
    }
}

✅ Explanation:

nested_schema.json should define the structure of nested objects.
schema.validate() ensures nested objects match the schema.

🚀 7. Best Practices for JSON Validation in Java

✅ Always Validate JSON Before Parsing: Avoid exceptions by verifying JSON syntax.
✅ Use Schema for Complex JSONs: For large JSON structures, define a strict schema.
✅ Catch Exceptions Gracefully: Wrap JSON operations in try-catch blocks.
✅ Consider Nested Validations: If your JSON contains nested objects, validate each level.

🕹️ 8. Common Errors and How to Handle Them

Error	Cause	Solution
`MismatchedInputException`	Incorrect JSON structure	Validate and match Java classes.
`JsonProcessingException`	Malformed JSON	Check JSON syntax.
`ValidationException`	Schema mismatch	Update JSON schema.

🎉 Conclusion: JSON Validation in Java – Mastered!

✅ You can now:

Validate JSON syntax with Jackson.
Use JSON Schema for advanced validation.
Catch errors and handle them gracefully.
Work confidently with complex JSON structures!

JSON Validation - potatoscript/json GitHub Wiki

✅ JSON Validation in Java: Ensure Your JSON is Correct! 🎯

🎯 What is JSON Validation?

🔥 1. Why Validate JSON?

🎁 Common Errors:

🧩 2. JSON Validation Methods in Java

⚡️ a) Basic Syntax Validation

📚 Add Jackson to Your Project

🎯 Example: Basic Syntax Validation with Jackson

📌 b) JSON Schema Validation

📚 Add JSON Schema Validator to Your Project

🎯 3. JSON Schema Basics

📄 Sample JSON Schema:

🎯 4. Validating JSON Against Schema in Java

🔥 Step 1: Create a JSON Schema File

🔥 Step 2: Validate JSON Using Everit Library

🎨 5. Custom JSON Validation with Jackson Annotations

🎯 Example: Using Jackson Annotations

🕵️‍♂️ 6. Validating Nested JSON in Java

🎯 Example: Nested JSON Validation

🚀 7. Best Practices for JSON Validation in Java

🕹️ 8. Common Errors and How to Handle Them

🎉 Conclusion: JSON Validation in Java – Mastered!

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