java - 通用 DAO、Spring、Hibernate

Question

我想了解如何在我的数据库上实现添加、编辑、删除和搜索等通用方法，我已经建立了连接( hibernate )并且工作正常

我确实有这个方法，有效

类:GenericDAO

public <T> T save(final T o){
        Session session=HibernateUtil.getSessionFactory().openSession();
        Transaction trans=session.beginTransaction();
        Object object = (T) session.save(o);
        trans.commit();
        return (T) object;
    }

和Main

GenericDAO gen = new GenericDAO();
gen.save(object); 

我还有其他方法，但我不知道如何使用它们

类:GenericDAO

public void delete(final Object object){
   Session session=HibernateUtil.getSessionFactory().openSession();
   Transaction trans=session.beginTransaction();
   session.delete(object);
   trans.commit();
}

/***/
public <T> T get(final Class<T> type, final int id){
    Session session=HibernateUtil.getSessionFactory().openSession();
    Transaction trans=session.beginTransaction();
    Object object = (T) session.get(type, id);
    trans.commit();
    return (T) object;
}

public <T> List<T> getAll(final Class<T> type) {
    Session session=HibernateUtil.getSessionFactory().openSession();
    Transaction trans=session.beginTransaction();
    final Criteria crit = session.createCriteria(type);
    List<T> list = crit.list();
    trans.commit();
    return list;
}

谢谢

Answer 1

我认为GenericDAO类是基类。它不是直接使用的。你检查过这篇文章吗？我检查了这篇文章并创建了一个示例项目。

• Don't repeat the DAO!

示例

GitHub - generic-dao-hibernate sample

例如，您可能希望创建一个 API 来根据 MySQL 第一步示例检索所有员工列表。

员工表架构如下:

基本 SQL

    CREATE TABLE employees (
        emp_no      INT             NOT NULL,  -- UNSIGNED AUTO_INCREMENT??
        birth_date  DATE            NOT NULL,
        first_name  VARCHAR(14)     NOT NULL,
        last_name   VARCHAR(16)     NOT NULL,
        gender      ENUM ('M','F')  NOT NULL,  -- Enumeration of either 'M' or 'F'  
        hire_date   DATE            NOT NULL,
        PRIMARY KEY (emp_no)                   -- Index built automatically on primary-key column
                                               -- INDEX (first_name)
                                               -- INDEX (last_name)
    );

对象/关系映射

Hibernate 要求您配置映射对象关系设置。之后，您将享受对象到 SQL 和 SQL 到对象的转换。

基于SQL的实体类

• @Entity, @Table, @Id, @Column, @GeneratedValue来自 Hibernate
• @Data, @NoArgsConstructor来自 lombok，它减少了 getter/setter 代码

• @XmlRootElement, @XmlAccessorType来自 jaxb，您可能不需要使用它

  @Entity
  @Data
  @NoArgsConstructor
  @Table(name = "employees")
  @XmlAccessorType(XmlAccessType.FIELD)
  @XmlRootElement
  public class Employees implements Serializable {
  
      private static final long serialVersionUID = 1L;
  
      @Id
      @Column(name = "emp_no", unique = true)
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      private Integer empNo;
  
      @Column(name = "birth_date")
      private Date birthDate;
  
      @Column(name = "first_name")
      private String firstName;
  
      @Column(name = "last_name")
      private String lastName;
  
      @Column(name = "gender")
      @Enumerated(EnumType.STRING)
      private Gender gender;
  
      @Column(name = "hire_date")
      private Date hireDate;
  }
  

前端资源类

您总是需要编写DAO(数据访问对象)来访问数据库。 GenericDAO是一种减少样板源代码的方法。

EmployeesResource 类

• WEB API 上的 CRUD 操作
  • #create , #read , #update或#delete

应该等同于

• SQL
  • INSERT , SELECT , UPDATE和DELETE

您需要使用 key 来识别一条或多条记录。在这种情况下，id是示例主键。

    @Path("/employee")
    public class EmployeesResource {

        static Logger log = LoggerFactory.getLogger(EmployeesResource.class);

        @GET
        @Produces(MediaType.APPLICATION_JSON)
        public List<Employees> index(@BeanParam Employees paramBean) {
            EmployeesDao dao = (EmployeesDao) SpringApplicationContext.getBean("employeesDao");
            List<Employees> result = dao.read();
            System.out.println("Get all employees: size = " + result.size());
            return result;
        }

        @GET
        @Path("{id}")
        @Produces(MediaType.APPLICATION_JSON)
        public Employees show(@PathParam("id") Integer id) {
            EmployeesDao dao = (EmployeesDao) SpringApplicationContext.getBean("employeesDao");
            System.out.println("Get employees -> id = " + id);
            return dao.read(id);
        }

        @POST
        @Consumes(MediaType.APPLICATION_JSON)
        public Integer create(Employees obj) {
            EmployeesDao dao = (EmployeesDao) SpringApplicationContext.getBean("employeesDao");
            return dao.create(obj);
        }

        @PUT
        @Path("{id}")
        @Consumes(MediaType.APPLICATION_JSON)
        public void update(Employees obj, @PathParam("id") String id) {
            EmployeesDao dao = (EmployeesDao) SpringApplicationContext.getBean("employeesDao");
            dao.update(obj);
        }

        @DELETE
        @Path("{id}")
        public void destroy(@PathParam("id") Integer id) throws Exception {
            EmployeesDao dao = (EmployeesDao) SpringApplicationContext.getBean("EmployeesDao");
            dao.delete(id);
        }
    }

GenericDao 接口(interface)和实现

界面(来自 ibm 的帖子)

根据帖子，我们可以声明dao接口(interface)。然后我们应该实现该接口(interface)的方法。

    public interface GenericDao<T, PK extends Serializable> {

        /** Persist the newInstance object into database */
        PK create(T newInstance);

        /**
         * Retrieve an object that was previously persisted to the database using
         * the indicated id as primary key
         */
        T read(PK id);
        List<T> read();

        /** Save changes made to a persistent object. */
        void update(T transientObject);

        /** Remove an object from persistent storage in the database */
        void delete(PK id) throws Exception;
        void delete(T persistentObject) throws Exception;
    }

实现

    public class GenericDaoHibernateImpl<T, PK extends Serializable> implements GenericDao<T, PK> {

        private Class<T> type;

        @Autowired
        private SessionFactory sessionFactory;

        public SessionFactory getSessionFactory() {
            return sessionFactory;
        }

        public void setSessionFactory(SessionFactory sessionFactory) {
            this.sessionFactory = sessionFactory;
        }

        public GenericDaoHibernateImpl(Class<T> type) {
            this.type = type;
        }

        // Not showing implementations of getSession() and setSessionFactory()
        private Session getSession() {
            Session session = sessionFactory.getCurrentSession();
            return session;
        }

        @Transactional(readOnly = false, rollbackFor = RuntimeException.class)
        public PK create(T o) {
            return (PK) getSession().save(o);
        }

        @Transactional(readOnly = false, rollbackFor = RuntimeException.class)
        public void update(T o) {
            getSession().update(o);
        }

        @Transactional(readOnly = true)
        public T read(PK id) {
            return (T) getSession().get(type, id);
        }

        @SuppressWarnings("unchecked")
        @Transactional(readOnly = true)
        public List<T> read() {
            return (List<T>) getSession().createCriteria(type).list();
        }

        @Transactional(readOnly = false, rollbackFor = RuntimeException.class)
        public void delete(PK id) {
            T o = getSession().load(type, id);
            getSession().delete(o);
        }

        @Transactional(readOnly = false, rollbackFor = RuntimeException.class)
        public void delete(T o) {
            getSession().delete(o);
        }

如果项目中只使用简单的CRUD操作，则不需要附加任何SQL操作的代码。例如，您可以创建另一个简单的 SQL 表，如 divisions_table或personnel_table使用extends GenericDao<Division, Integer>或extends GenericDao<Personnel, Integer> .

编辑

要实例化与每个表相关的真实dao类，需要配置applicationContext.xml还有 bean 。

示例

<bean id="employeesDao" parent="abstractDao">
    <!-- You need to configure the interface for Dao -->
    <property name="proxyInterfaces">
        <value>jp.gr.java_conf.hangedman.dao.EmployeesDao</value>
    </property>
    <property name="target">
        <bean parent="abstractDaoTarget">
            <constructor-arg>
                <value>jp.gr.java_conf.hangedman.models.Employees</value>
            </constructor-arg>
        </bean>
    </property>
</bean>

附注

您需要记住这篇文章是十年前写的。而且，你应该认真考虑哪个 O/R 映射器真的好还是不好。我认为 O/R 映射器现在正在略有下降。您可以找到 MyBatis 而不是 Hibernate , JOOQ