Hibernate中的通用DAO模式

Umesh我将向您展示我们如何实现此功能

介面

public interface Repository<INSTANCE_CLASS, PRIMARY_KEY_CLASS> {    void add(INSTANCE_CLASS instance);    void merge(INSTANCE_CLASS instance);    void remove(PRIMARY_KEY_CLASS id);    INSTANCE_CLASS findById(PRIMARY_KEY_CLASS id);    INSTANCE_CLASS findById(PRIMARY_KEY_CLASS id, Class fetchingStrategy, Object... args);    List<INSTANCE_CLASS> findAll();    List<INSTANCE_CLASS> findAll(Class fetchingStrategy, Object... args);    List<INSTANCE_CLASS> findAll(int pageNumber, int pageSize);    List<INSTANCE_CLASS> findAll(int pageNumber, int pageSize, Class fetchingStrategy, Object... args);    List<INSTANCE_CLASS> findAllByCriteria(Criteria criteria);    List<INSTANCE_CLASS> findAllByCriteria(Criteria criteria, Class fetchingStrategy, Object... args);    List<INSTANCE_CLASS> findAllByCriteria(int pageNumber, int pageSize, Criteria criteria);    List<INSTANCE_CLASS> findAllByCriteria(int pageNumber, int pageSize, Criteria criteria, Class fetchingStrategy, Object... args);}

因为您通常不需要上面显示的所有方法，所以我们创建一个抽象类 是为了作为一个虚拟实现。

public abstract class AbstractRepository<INSTANCE_CLASS, PRIMARY_KEY_CLASS> implements Repository<INSTANCE_CLASS, PRIMARY_KEY_CLASS> {    public void add(INSTANCE_CLASS instance) {        throw new UnsupportedOperationException("Not supported yet.");    }    public void merge(INSTANCE_CLASS instance) {        throw new UnsupportedOperationException("Not supported yet.");    }    public void remove(PRIMARY_KEY_CLASS id) {        throw new UnsupportedOperationException("Not supported yet.");    }    public INSTANCE_CLASS findById(PRIMARY_KEY_CLASS id) {        throw new UnsupportedOperationException("Not supported yet.");    }    public INSTANCE_CLASS findById(PRIMARY_KEY_CLASS id, Class fetchingStrategy, Object... args) {        throw new UnsupportedOperationException("Not supported yet.");    }    public List<INSTANCE_CLASS> findAll() {        throw new UnsupportedOperationException("Not supported yet.");    }    public List<INSTANCE_CLASS> findAll(Class fetchingStrategy, Object... args) {        throw new UnsupportedOperationException("Not supported yet.");    }    public List<INSTANCE_CLASS> findAll(int pageNumber, int pageSize) {        throw new UnsupportedOperationException("Not supported yet.");    }    public List<INSTANCE_CLASS> findAll(int pageNumber, int pageSize, Class fetchingStrategy, Object... args) {        throw new UnsupportedOperationException("Not supported yet.");    }    public List<INSTANCE_CLASS> findAllByCriteria(Criteria criteria) {        throw new UnsupportedOperationException("Not supported yet.");    }    public List<INSTANCE_CLASS> findAllByCriteria(Criteria criteria, Class fetchingStrategy, Object... args) {        throw new UnsupportedOperationException("Not supported yet.");    }    public List<INSTANCE_CLASS> findAllByCriteria(int pageNumber, int pageSize, Criteria criteria) {        throw new UnsupportedOperationException("Not supported yet.");    }    public List<INSTANCE_CLASS> findAllByCriteria(int pageNumber, int pageSize, Criteria criteria, Class fetchingStrategy, Object... args) {        throw new UnsupportedOperationException("Not supported yet.");    }}

现在，例如，如果您想要一个仅需要添加方法的存储库，则可以使用

public class PersonRepository extends AbstractRepository<Person, Integer> {    public void add(Person instance) {                }}

如果其他开发人员尝试访问除添加方法以外的其他方法，则他或她将获得 UnsupportedOperationException

条件 只是标记界面 。

public interface Criteria {}

一些方法定义参数类fetchingStrategy的目的 是匹配外部化的命名查询 。这样，我避免了容易出错的手工编码字符串。例如，JSR-303
bean验证使用此方法来验证属性 组
。看这里

public class Person {    public static interface PERSON_WITH_ADDRESS {}}

外部化命名查询如下所示

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping>    <query name="PERSON_WITH_ADDRESS">        <![CDATA[ from      Person p left join fetch      p.address        ]]>    </query></hibernate-mapping>

因此，当我想检索所有具有地址的人时，我打电话

PersonRepository<Person, Integer> respository ...List<Person> personList = repository.findAll(PERSON_WITH_ADDRESS.class);

findAll可以写成

public class PersonRepository extends AbstractRepository<Person, Integer> {    List<Person> findAll(Class fetchingStrategy, Object... args) {        if(fetchingStrategy.isAssignableFrom(PERSON_WITH_ADDRESS.class)) { sessionFactory.getCurrentSession()    .getNamedQuery(fetchingStrategy.getSimpleName())    .list();        }        throw new UnsupportedOperationException("Not supported yet.");    }}