# Modeling an RDF Resource The following content highlights the key modifications to a Java class to convert it into an [RDF resource](https://docs.inrupt.com/reference/glossary#rdf-resource) class. As a starting point, consider a non-RDF class **`Expense`**. Such a class may be implemented similarly to the following sample code: ```java // Non-RDF Class public class Expense { private UUID _id; private Date date; private String description; // ... Additional fields public Expense() { } public Expense(date, description, //...) { this.date = date; this.description = descriptions; //... } public Date getDate() { return date; } public void setDate(Date date) { this.date = date; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } // ... Additional getters/setters and other content } ``` ### 1. Extend the SolidRDFSource The [SolidRDFSource](https://api.docs.inrupt.com/docs/developer-tools/api/java/inrupt-client/latest/com/inrupt/client/solid/SolidRDFSource.html) class maps to an RDF resource. A summary of parameters to the [SolidRDFSource](https://api.docs.inrupt.com/docs/developer-tools/api/java/inrupt-client/latest/com/inrupt/client/solid/SolidRDFSource.html) class constructors are as follows:
FieldTypeDescription
identifierjava.net.URIThe URI (Uniform Resource Identifier) of the resource.
datasetorg.apache.commons.rdf.api.DatasetThe RDF dataset (i.e., the sets of triples) contained in the resource.
headerscom.inrupt.client.HeadersCollection of HTTP headers.
To model the **`Expense`** class as an RDF resource, the class: * Extends the [SolidRDFSource](https://api.docs.inrupt.com/docs/developer-tools/api/java/inrupt-client/latest/com/inrupt/client/solid/SolidRDFSource.html) and * Adds constructors for the [SolidRDFSource](https://api.docs.inrupt.com/docs/developer-tools/api/java/inrupt-client/latest/com/inrupt/client/solid/SolidRDFSource.html) fields (**`identifier`**, **`dataset`**, **`headers`**). ```java public class Expense extends SolidRDFSource { private final Node subject; // ... public Expense(final URI identifier, final Dataset dataset, final Headers headers) { super(identifier, dataset, headers); // ... } public Expense(final URI identifier) { this(identifier, null, null); } public Expense(final URI identifier, String merchantProvider, Date expenseDate, String description, BigDecimal amount, String currency, String category) { this(identifier, null, null); //... } } ``` {% hint style="warning" %} The SolidRDFSource constructor that accepts Metadata as a parameter (instead of Headers) has been deprecated. {% endhint %} ### 2. Inner Class that Extends WrapperIRI A sample RDF file that for a sample Expense data is shown below in [Turtle format](https://docs.inrupt.com/reference/glossary#turtle): ```turtle ; "2023-03-07T00:00:00Z"^^ ; "Example Restaurant" ; "Team Lunch" ; "Travel and Entertainment" ; "USD" ; "120"^^ ; . ``` where:
subjectURL<https://pod.example.com/container/expenses/202303/teamlunch>
predicatesURL
  • <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
  • <https://schema.org/purchaseDate>
  • <https://schema.org/provider>
  • etc.
objectsLiterals or URLS
  • "2023-03-07T00:00:00Z"^^<http://www.w3.org/2001/XMLSchema#dateTime>
  • "Example Restaurant",
  • <https://pod.example.com/expenses/receipt1.jpg>
  • etc.
To handle the mapping of the expense data (date, provider, description, category, priceCurrency, total) to RDF triples (**` `**): * The **`Expense`** class defines the predicate IRIs. That is, instead of having a Class field named **`date`**, for the RDF Resource, the value of the field is mapped to the IRI **`"https://schema.org/purchaseDate"`**. * The **`Expense`** class defines an inner class **`Node`** that extends the [WrapperIRI](https://api.docs.inrupt.com/docs/developer-tools/api/java/inrupt-client/latest/com/inrupt/rdf/wrapping/commons/WrapperIRI.html) class. ```java public class Expense extends SolidRDFSource { // ... static IRI SCHEMA_DATE = rdf.createIRI("https://schema.org/purchaseDate"); static IRI SCHEMA_PROVIDER = rdf.createIRI("https://schema.org/provider"); static IRI SCHEMA_DESCRIPTION = rdf.createIRI("https://schema.org/description"); static IRI SCHEMA_TOTAL_PRICE = rdf.createIRI("https://schema.org/totalPrice"); static IRI SCHEMA_CURRENCY = rdf.createIRI("https://schema.org/priceCurrency"); static IRI SCHEMA_CATEGORY = rdf.createIRI("https://schema.org/category"); static IRI SCHEMA_IMAGE = rdf.createIRI("https://schema.org/image"); // ... class Node extends WrapperIRI { Node(final RDFTerm original, final Graph graph) { super(original, graph); } URI getRDFType() { return anyOrNull(RDF_TYPE, ValueMappings::iriAsUri); } void setRDFType(String type) { overwriteNullable(RDF_TYPE, type, TermMappings::asIri); } String getMerchantProvider() { return anyOrNull(SCHEMA_PROVIDER, ValueMappings::literalAsString); } String getMerchantProvider() { return anyOrNull(SCHEMA_PROVIDER, ValueMappings::literalAsString); } void setMerchantProvider(String provider) { overwriteNullable(SCHEMA_PROVIDER, provider, TermMappings::asStringLiteral); } // ... } } ``` ### Add the Inner Class Field to the RDF Resource Class To use the defined mappings in the inner class: * Update **`Expense.java`** to include a new field **`subject`** set to the inner class **`Node`**. * Update the **`Expense.java`** getters and setters to use the **`subject`**‘s getters and setters. ```java public class Expense extends SolidRDFSource { // ... private final Node subject; // ... public URI getRDFType() { return subject.getRDFType(); } public void setRdfType(String rdfType) { subject.setRDFType(rdfType); } public String getMerchantProvider() { return subject.getMerchantProvider(); } public void setMerchantProvider(String merchantProvider) { subject.setMerchantProvider(merchantProvider); } public Date getExpenseDate() { return subject.getExpenseDate(); } public void setExpenseDate(Date expenseDate) { subject.setExpenseDate(expenseDate); } //... } ```