JAVA-JPA-Setting

JPA (Java Persistence API)

• Java 持久化 API

• 是 Java 對 ORM(Object-Relation Mapping) 做出的規範，一個介面(Interface)

• 讓 Model class跟 DB Table 做映射,取代直接跟 DB要資料

• 以 hibernate實作 JPA

• 設定 persistence.xml

  <?xml version="1.0" encoding="UTF-8"?>
  <persistence version="1.0" 
  xmlns="http://java.sun.com/xml/ns/persistence" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="ContactPU" transaction-type="RESOURCE_LOCAL">
      <provider>org.hibernate.ejb.HibernatePersistence</provider>
      <class>Contact.Contact</class>
      <properties>
      <property name="hibernate.cache.provider_class" value="org.hibernate.cache.NoCacheProvider"/>
      <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
      <property name="hibernate.connection.url" value="jdbc:mysql://資料庫-IP:資料庫服務-TCP-埠號/資料庫名稱"/>
      <property name="hibernate.connection.username" value="資料庫帳號"/>
      <property name="hibernate.connection.password" value="資料庫密碼"/>
      </properties>
  </persistence-unit>
  </persistence>

• 建立 Table 對 物件的映射

  @Entity
  public class Customer {
      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      private Long id;
      private String name;
      private String email;
      private String address;
      
      protected Customer() {
          
      }
      
      protected Customer(String name,String email,String address) {
          this.name = name;
          this.address = address;
          this.email = email;		
      }
      
      public Long getId() {
          return this.id;
      }
  
      public String getName() {
          return this.name;
      }
      public void setName(String name) {
          this.name=name;
      }
      
      public String getEmail() {
          return this.email;
      }
      public void setEmail(String email) {
          this.email=email;
      }
      
      public String getAddress() {
          return this.address;
      }
      public void setAddress(String address) {
          this.address=address;
      }
  
  }

• 建立 CrudRepository

  public interface CustomerRepository extends CrudRepository<Customer, Long>{
  
      //要做複雜的 Query
      @Query(value = 
              "SELECT c "
              + "FROM Customer c "
              + "WHERE c.name LIKE '%' || :keyword || '%'"
              + " OR c.email LIKE '%' || :keyword || '%'"
              + " OR c.address LIKE '%' || :keyword || '%'")
      public List<Customer> search(@Param("keyword") String keyword);
  }

• 建立 Service

  @Service
  @Transactional
  public class CustomerService {
      @Autowired CustomerRepository repo;
      
      public void save(Customer customer) {
          repo.save(customer);		
      }
      
      public List<Customer> listAll() {
          return (List<Customer>)repo.findAll();		
      }
      
      public Customer get(Long Id) {
          return repo.findById(Id).get();
      }
      
      public void delete(Long Id) {
          repo.deleteById(Id);
      }
      
      public List<Customer> search(String keyword) {
          return repo.search(keyword);
      }
  }