Przykładowe klasy z tutoriala

https://spring.io/guides/gs/accessing-data-jpa/

PC51-SpringDataH2/src/main/java/com/example/demo/Customer.java

+package com.example.demo;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+
+@Entity
+public class Customer {
+
+  @Id
+  @GeneratedValue(strategy=GenerationType.AUTO)
+  private Long id;
+  private String firstName;
+  private String lastName;
+
+  protected Customer() {}
+
+  public Customer(String firstName, String lastName) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
+  @Override
+  public String toString() {
+    return String.format(
+        "Customer[id=%d, firstName='%s', lastName='%s']",
+        id, firstName, lastName);
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public String getLastName() {
+    return lastName;
+  }
+}
\ No newline at end of file

PC51-SpringDataH2/src/main/java/com/example/demo/CustomerRepository.java

+package com.example.demo;
+
+import java.util.List;
+
+import org.springframework.data.repository.CrudRepository;
+
+public interface CustomerRepository extends CrudRepository<Customer, Long> {
+
+  List<Customer> findByLastName(String lastName);
+
+  Customer findById(long id);
+}
\ No newline at end of file

PC51-SpringDataH2/src/main/java/com/example/demo/Pc51SpringDataH2Application.java

 package com.example.demo;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.CommandLineRunner;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.Bean;
 
 @SpringBootApplication
 public class Pc51SpringDataH2Application {
 
-	public static void main(String[] args) {
-		SpringApplication.run(Pc51SpringDataH2Application.class, args);
-	}
+    public static void main(String[] args) {
+        SpringApplication.run(Pc51SpringDataH2Application.class, args);
+    }
+
+	private static final Logger log = LoggerFactory.getLogger(Pc51SpringDataH2Application.class);
+
+	@Bean
+	public CommandLineRunner demo(CustomerRepository repository) {
+	    return (args) -> {
+	      // save a few customers
+	      repository.save(new Customer("Jack", "Bauer"));
+	      repository.save(new Customer("Chloe", "O'Brian"));
+	      repository.save(new Customer("Kim", "Bauer"));
+	      repository.save(new Customer("David", "Palmer"));
+	      repository.save(new Customer("Michelle", "Dessler"));
 
+	      // fetch all customers
+	      log.info("Customers found with findAll():");
+	      log.info("-------------------------------");
+	      for (Customer customer : repository.findAll()) {
+	        log.info(customer.toString());
+	      }
+	      log.info("");
+
+	      // fetch an individual customer by ID
+	      Customer customer = repository.findById(1L);
+	      log.info("Customer found with findById(1L):");
+	      log.info("--------------------------------");
+	      log.info(customer.toString());
+	      log.info("");
+
+	      // fetch customers by last name
+	      log.info("Customer found with findByLastName('Bauer'):");
+	      log.info("--------------------------------------------");
+	      repository.findByLastName("Bauer").forEach(bauer -> {
+	        log.info(bauer.toString());
+	      });
+	      // for (Customer bauer : repository.findByLastName("Bauer")) {
+	      //  log.info(bauer.toString());
+	      // }
+	      log.info("");
+	    };
+	}
 }