Accessing Data with JPA

引入依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
        
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
</dependency>

定义数据库实体

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.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;
    }
    
    //Get/Set略public String toString() {
        return String.format("Customer[id=%d,  firstName='%s', lastName='%s']", id, firstName, lastName);
    }
}

定义仓库接口

import org.springframework.data.repository.CrudRepository;

import com.aaron.springBootDemo.domain.Customer;

public interface CustomerRepository extends CrudRepository<Customer, Long> {

    List<Customer> findByLastName(String lastName);
}

定义Controller

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.aaron.springBootDemo.domain.Customer;
import com.aaron.springBootDemo.service.CustomerRepository;

@RestController
public class JpaController {
    
    private final Logger LOG = LoggerFactory.getLogger(JpaController.class);
    
    @Autowired
    private CustomerRepository repository;
    
    @Bean
    public CommandLineRunner demo(CustomerRepository repository) {
        return (args) -> {
            repository.save(new Customer("Jack", "Bauer"));
            repository.save(new Customer("Chloe", "O'Brain"));
            repository.save(new Customer("Kim", "Bauer"));
            repository.save(new Customer("David", "Palmer"));
            repository.save(new Customer("Michelle", "Dessler"));
            
            for(Customer c : repository.findAll()) {
                LOG.info("findAll " + c.toString());
            }
            
            repository.findById(1L).ifPresent(customer -> {
                LOG.info("findById " + customer.toString());
            });
            
            repository.findByLastName("Bauer").forEach(bauer -> {
                LOG.info("findByLastName " + bauer.toString());
            });
        };
    }

    @RequestMapping("/getCustomerById")
    public Customer getCustomerById(@RequestParam(value="id", defaultValue="1") Long id) {
        return repository.findById(id).get();
    }
}