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juneau-examples-core

The juneau-examples-core module provides practical examples demonstrating how to use Apache Juneau's core marshalling capabilities for serialization and deserialization of Plain Old Java Objects (POJOs).

Overview​

This module focuses on the fundamental serialization and deserialization features of Juneau Core, showing developers how to:

  • Convert POJOs to various content types (JSON, XML, RDF)
  • Parse content back into POJOs
  • Configure serializers and parsers with different properties
  • Handle complex object structures

Getting Started​

To use the examples in this module, add the following dependency to your project:

<dependency>
    <groupId>org.apache.juneau</groupId>
    <artifactId>juneau-core</artifactId>
    <version>${juneau.version}</version>
</dependency>

Example Categories​

JSON Examples​

Juneau provides comprehensive JSON support out of the box, allowing you to read and write JSON structures into POJOs with minimal configuration.

JsonSimpleExample.java​

Demonstrates basic usage of JsonSerializer and JsonParser to convert POJOs to JSON strings and back to POJOs.

Key Features:

  • Simple POJO serialization to JSON
  • JSON parsing back to POJOs
  • Automatic type inference
  • Null handling

JsonConfigurationExample.java​

Shows how to create JsonParser and JsonSerializer instances with custom configuration properties.

Key Features:

  • Custom serializer/parser configuration
  • Property customization
  • Formatting options
  • Validation settings

XML Examples​

Juneau's XML support enables seamless conversion between POJOs and XML structures.

XmlComplexExample.java​

Demonstrates how to use XmlSerializer and XmlParser to handle complex POJOs with nested objects and collections.

Key Features:

  • Complex object serialization to XML
  • Nested object handling
  • Collection serialization
  • XML namespace support

RDF Examples​

For RDF support, Juneau integrates with Apache Jena to provide RDF serialization capabilities.

Prerequisites​

Add Apache Jena to your classpath:

<dependency>
    <groupId>org.apache.jena</groupId>
    <artifactId>jena-core</artifactId>
    <version>${jena.version}</version> <!-- Juneau is tested against 2.7.1 -->
</dependency>

RDF Support​

RDF serialization support is available through the juneau-marshall-rdf module. While there isn't a dedicated example file, RDF functionality can be demonstrated using the existing serializers with RDF-specific configurations.

Key Features:

  • POJO to RDF conversion
  • Multiple RDF formats (RDF/XML, N3, NTriple, Turtle)
  • RDF vocabulary mapping
  • Semantic web integration
RDF Examples

RDF examples are integrated into the core serialization examples rather than having separate dedicated example files.

Running the Examples​

All examples in this module are designed to be run as standalone Java applications. Each example class contains a main method that demonstrates the specific functionality.

Example Structure​

public class ExampleClass {
    public static void main(String[] args) {
        // Example implementation
        // Demonstrates specific Juneau functionality
    }
}

Common Patterns​

The examples follow these common patterns:

  1. Create POJOs - Define simple or complex Java objects
  2. Configure Serializers/Parsers - Set up Juneau components with desired properties
  3. Serialize - Convert POJOs to target format (JSON, XML, RDF)
  4. Parse - Convert formatted strings back to POJOs
  5. Validate - Ensure data integrity throughout the process

Best Practices​

Performance Considerations​

  • Reuse serializer/parser instances when possible
  • Configure appropriate buffer sizes for large objects
  • Use streaming for very large datasets

Error Handling​

  • Always handle serialization/parsing exceptions
  • Validate input data before processing
  • Use appropriate logging for debugging

Configuration​

  • Start with default configurations
  • Customize only when necessary
  • Document custom configurations

Integration with Other Modules​

The examples in this module serve as the foundation for more complex scenarios found in:

juneau-examples-rest - REST API examples using these core conceptsjuneau-petstore - Complete application demonstrating end-to-end usagejuneau-microservice - Microservice examples building on core serialization Juneau Marshall Basics - Core marshalling conceptsJuneau Ecosystem Overview - Overall framework architecturejuneau-examples-rest - REST-specific examples

Source Code​

The complete source code for all examples is available in the juneau-examples-core module of the Apache Juneau project.

Contributing​

To contribute new examples or improve existing ones:

  1. Follow the established patterns in existing examples
  2. Include comprehensive comments and documentation
  3. Test examples with various data scenarios
  4. Update this documentation when adding new examples