Spring MVC：通用的DAO和服务类 [英] Spring MVC: Generic DAO and Service classes

问题描述

我在Spring MVC中写web。我使用Generic DAO编写了所有DAO。现在我想重写我的Service类。如何写通用服务？

有我的DAO：

  / * ################################# DAO ########### ##################### * / 
 package net.example.com.dao; 
 
 import java.util.List; 
 
 public interface GenericDao< T> {
 public T findById（int id）; 
 public List< T>找到所有（）; 
 public void update（T entity）; 
 public void save（T entity）; 
 public void delete（T entity）; 
} 
 
 / * ----------------------------------- ------------------- * / 
 
 package net.example.com.dao; 
 
 import java.io.Serializable; 
 import java.util.List; 
 
 import org.hibernate.Session; 
 import org.hibernate.SessionFactory; 
 import org.springframework.beans.factory.annotation.Autowired; 
 import org.springframework.context.annotation.Scope; 
 
 @Scope（prototype）
公共抽象类GenericHibernateDaoImpl< T extends Serializable>实现GenericDao< T> {
 
私人课程< T> clazz中; 
 
 @Autowired 
 private SessionFactory sessionFactory; 
 
 public final void setClazz（Class< T> clazzToSet）{
 this.clazz = clazzToSet; 
} 
 
 @SuppressWarnings（unchecked）
 public T findById（int id）{
 return（T）getCurrentSession（）。get（clazz，id） ; 
} 
 
 @SuppressWarnings（unchecked）
 public List< T> findAll（）{
 return getCurrentSession（）。createQuery（FROM+ clazz.getName（））。list（）; 
} 
 
 public void update（T entity）{
 getCurrentSession（）。update（entity）; 
} 
 
 public void save（T entity）{
 getCurrentSession（）。save（entity）; 
} 
 
 public void delete（T entity）{
 getCurrentSession（）。delete（entity）; 
} 
 
 protected final session getCurrentSession（）{
 return sessionFactory.getCurrentSession（）; 
} 
} 
 
 / * ------------------------------ ------------------------ * / 
 
包net.example.com.dao; 
 
导入net.example.com.entity.Country; 
 
 public interface CountryDao extends GenericDao< Country> {
 
 public Country findByName（String name）; 
 public Country findByCode（String code）; 
 
} 
 
 / * ------------------------------- ----------------------- * / 
 
 package net.example.com.dao; 
 
 import org.springframework.stereotype.Repository; 
 
导入net.example.com.entity.Country; 
 
 @Repository 
 public class CountryDaoImpl extends GenericHibernateDaoImpl< Country> implements CountryDao {
 
 @Override 
 public Country findByName（String name）{
 return（Country）getCurrentSession（）
 .createQuery（FROM Country WHERE name =名称）
 .setString（name，name）.uniqueResult（）; 
 
 $ b @Override 
 public Country findByCode（String code）{
 return（Country）getCurrentSession（）
 .createQuery（FROM Country WHERE code =：code）
 .setString（code，code）.uniqueResult（）; 
} 
 
} 
 
 / * ########################## ####### DAO ################################ * / 
  
 
 $ b 
和服务：
 
 
  / * ################################# SERVICE ################ ################ * / 
 
 package net.example.com.service; 
 
 import java.util.List; 
 
公共接口GenericManager< T> {// GenericManager< T>与GenericDao< T>相同。 
 
 public T findById（int id）; 
 public List< T>找到所有（）; 
 public void update（T entity）; 
 public void save（T entity）; 
 public void delete（T entity）; 
} 
 
 / * ----------------------------------- ------------------- * / 
 
 package net.example.com.service; 
 
 import java.util.List; 
 
 import org.springframework.beans.factory.annotation.Autowired; 
 import org.springframework.stereotype.Service; 
 
导入net.example.com.dao.GenericDao; 
 
 @Service 
公共抽象类GenericManagerImpl< T>实现GenericManager< T> {
 
 @Autowired 
保护GenericDao< T>道; 
 
 @Override 
 public T findById（int id）{
 return dao.findById（id）; 
} 
 
 @Override 
 public List< T> findAll（）{
 return dao.findAll（）; 
} 
 
 @Override 
 public void update（T entity）{
 dao.update（entity）; 
} 
 
 @Override 
 public void save（T entity）{
 dao.save（entity）; 
} 
 
 @Override 
 public void delete（T entity）{
 dao.delete（entity）; 
} 
} 
 / * ---------------------------------- -------------------- * / 
 
 package net.example.com.dao; 
 
导入net.example.com.entity.Country; 
 
公共接口CountryManager扩展了GenericDao< Country> {// CountryManager与CountryDao相同
 
 public Country findByName（String name）; 
 public Country findByCode（String code）; 
} 
 
 / * ----------------------------------- ------------------- * / 
 
 package net.example.com.service; 
 
 import java.util.List; 
 
 import javax.transaction.Transactional; 
 
 import org.springframework.beans.factory.annotation.Autowired; 
 import org.springframework.stereotype.Service; 
 
 import net.example.com.dao.CountryDao; 
 import net.example.com.entity.Country; 
 
 @Service 
 @Transactional 
 public class CountryManagerImpl extends GenericManagerImpl< Country>实现CountryManager {
 
 @覆盖
公共列表< Country> findAll（）{
 return dao.findAll（）; 
} 
 
 public国家findById（int id）{
返回dao.findById（id）; 
} 
 
 @Override 
 public Country findByName（String name）{
 return dao.findByName（name）; //编译器（和Eclipse）没有看到findByName !!!!!!!!! 
} 
 
 @Override 
 public Country findByCode（String code）{
 return dao.findByCode（code）; //编译器（和Eclipse）没有看到findByCode !!!!!!!!! 
} 
 
 @Override 
 public void save（Country country）{
 dao.save（country）; 
} 
 
 @Override 
 public void delete（Country country）{
 dao.delete（country）; 
} 
 
 @Override 
 public void update（Country country）{
 dao.update（country）; 
} 
 
} 
 
 / * -------------------------- ---------------------------- * / 
 
 / * ########## ####################### SERVICE ##########################编译器（和Eclipse）没有看到 
 ###### * / 
 > findByName 和 findByCode 方法。我明白为什么。但是我该如何重写呢？   解决方案

问题是，您的GenericDao直接注入到您的GenericManager中，但没有一个是具体的Spring bean，你将永远无法使用你的特定CountryDao。

你不能autowire GenericDao，只能定义它并提供setter：

  //将DAO作为genric参数添加
 public abstract class GenericManagerImpl< T，D extends GenericDao< T>>实现GenericManager< T> {
 private D dao; 
 
保护无效setDao（D dao）{
 this.dao = dao; 
} 
 
 ... 
  

}

然后，你将不得不在你的具体服务中注入一个混凝土spring bean。即在 CountryManagerImpl 中：

  //使用具体的DAO实例化具体服务
 public class CountryManagerImpl扩展了GenericManagerImpl< Country，CountryDao>实现CountryManager {
 
 //不要在这里重新声明你的dao以保留继承的
 
 //不要忘记注入
 @Inject（ countryDao）
 @Override 
 protected void setDao（CountryDao dao）{
 this.dao = dao; 
} 
 
 ... 
 
} 
  

然后，您将拥有一个完整的spring bean，并注入具体的CountryDao类型及其具体方法。

您可以看看我们在RESThub项目上做了什么关于通用服务： https://github.com/resthub/resthub-spring-stack/blob/master/resthub-common/src/main/java/org/resthub/common/service/CrudServiceImpl.java 和一些具体的例子： https://github.com/resthub/todo-backbone-example/blob/master/src/main/java/todo/TodoController.java （使用控制器而不是服务，但它是相似的） p>

希望它有帮助。

（如果有一些拼写错误，我不能现在仔细检查）

，顺便说一句，您应该考虑使用Spring Data而不是使用GenericDaos，但您仍然会对服务有相同的需求。

I am writting web in Spring MVC. I wrote all DAOs using Generic DAO. Now I would like to rewrite my Service classes. How can I write "Generic Service"?

There are my DAOs:

/* ################################# DAO ################################ */
package net.example.com.dao;

import java.util.List;

public interface GenericDao<T> {       
        public T findById(int id);     
        public List<T> findAll();      
        public void update(T entity);  
        public void save(T entity);    
        public void delete(T entity);
}

/* ------------------------------------------------------ */

package net.example.com.dao;

import java.io.Serializable;
import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Scope;

@Scope("prototype")
public abstract class GenericHibernateDaoImpl<T extends Serializable> implements GenericDao<T> {

        private Class<T> clazz;

        @Autowired
        private SessionFactory sessionFactory;

        public final void setClazz(Class<T> clazzToSet) {
                this.clazz = clazzToSet;               
        }

        @SuppressWarnings("unchecked")
        public T findById(int id) {
                return (T) getCurrentSession().get(clazz, id);
        }

        @SuppressWarnings("unchecked")
        public List<T> findAll() {
                return getCurrentSession().createQuery("FROM " + clazz.getName()).list();              
        }

        public void update(T entity) {
                getCurrentSession().update(entity);            
        }

        public void save(T entity) {
                getCurrentSession().save(entity);              
        }

        public void delete(T entity) {
                getCurrentSession().delete(entity);            
        }

        protected final Session getCurrentSession(){
                return sessionFactory.getCurrentSession();
        }
}

/* ------------------------------------------------------ */

package net.example.com.dao;

import net.example.com.entity.Country;

public interface CountryDao extends GenericDao<Country> {

    public Country findByName(String name);    
    public Country findByCode(String code);

}

/* ------------------------------------------------------ */

package net.example.com.dao;

import org.springframework.stereotype.Repository;

import net.example.com.entity.Country;

@Repository
public class CountryDaoImpl extends GenericHibernateDaoImpl<Country> implements CountryDao {

        @Override
        public Country findByName(String name) {
                return (Country) getCurrentSession()
                                .createQuery("FROM Country WHERE name = :name")
                                .setString("name", name).uniqueResult();
        }

        @Override
        public Country findByCode(String code) {
                return (Country) getCurrentSession()
                                .createQuery("FROM Country WHERE code = :code")
                                .setString("code", code).uniqueResult();
        }

}

/* ################################# DAO ################################ */

and Services:

/* ################################# SERVICE ################################ */

package net.example.com.service;

import java.util.List;

public interface GenericManager<T> { // GenericManager<T> is the same as GenericDao<T>

        public T findById(int id);     
        public List<T> findAll();      
        public void update(T entity);  
        public void save(T entity);    
        public void delete(T entity);
}

/* ------------------------------------------------------ */

package net.example.com.service;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import net.example.com.dao.GenericDao;

@Service
public abstract class GenericManagerImpl<T> implements GenericManager<T> {

        @Autowired
        protected GenericDao<T> dao;

        @Override
        public T findById(int id) {
                return dao.findById(id);
        }

        @Override
        public List<T> findAll() {
                return dao.findAll();
        }

        @Override
        public void update(T entity) {
                dao.update(entity);
        }

        @Override
        public void save(T entity) {
                dao.save(entity);
        }

        @Override
        public void delete(T entity) {
                dao.delete(entity);    
        }
}
/* ------------------------------------------------------ */

package net.example.com.dao;

import net.example.com.entity.Country;

public interface CountryManager extends GenericDao<Country> { // CountryManager is the same as CountryDao

    public Country findByName(String name);    
    public Country findByCode(String code);
}

/* ------------------------------------------------------ */

package net.example.com.service;

import java.util.List;

import javax.transaction.Transactional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import net.example.com.dao.CountryDao;
import net.example.com.entity.Country;

@Service
@Transactional
public class CountryManagerImpl extends GenericManagerImpl<Country> implements CountryManager {

        @Override
        public List<Country> findAll() {
                return dao.findAll();
        }

        public Country findById(int id) {
                return dao.findById(id);
        }

        @Override
        public Country findByName(String name) {
                return dao.findByName(name); // compiler (and Eclipse) do not see findByName !!!!!!!!!
        }

        @Override
        public Country findByCode(String code) {
                return dao.findByCode(code); // compiler (and Eclipse) do not see findByCode !!!!!!!!!
        }

        @Override
        public void save(Country country) {
                dao.save(country);
        }

        @Override
        public void delete(Country country) {
                dao.delete(country);
        }

        @Override
        public void update(Country country) {
                dao.update(country);
        }

}

/* ------------------------------------------------------ */

/* ################################# SERVICE ################################ */

Compiler (and Eclipse) do not see findByName and findByCode methods. I understand why. But how can I rewrite it?

解决方案

The problem is that your inject directly your GenericDao in your GenericManager but none of them is a concrete Spring bean and you will never be able to use your specific CountryDao.

You must not autowire GenericDao but only define it and provide setter :

// Add DAO as a genric parameter
public abstract class GenericManagerImpl<T, D extends GenericDao<T>> implements GenericManager<T> {
    private D dao;

    protected void setDao (D dao) {
        this.dao = dao;
    }

...

}

Then, you will have to inject a concrete spring bean in your concrete services. i.e. in CountryManagerImpl:

// Instantiate your concrete service with your concrete DAO
public class CountryManagerImpl extends GenericManagerImpl<Country, CountryDao> implements CountryManager {

    // Do not redeclare your dao here in order to keep the inherited one

    // Don't forget to inject
    @Inject("countryDao")
    @Override
    protected void setDao (CountryDao dao) {
        this.dao = dao;
    }

...

}

You will have then a full spring bean injected with your concrete CountryDao type and its specific methods.

You can take a look at what we did on RESThub project regarding generic services : https://github.com/resthub/resthub-spring-stack/blob/master/resthub-common/src/main/java/org/resthub/common/service/CrudServiceImpl.java and some concrete example : https://github.com/resthub/todo-backbone-example/blob/master/src/main/java/todo/TodoController.java (with a Controller instead of a Service but it is similar)

Hope it will help.

(and sorry if there is some typos, I cannot double check right now)

and, BTW, you should consider using Spring Data instead of using GenericDaos but you will still have the same needs regarding your Services.

这篇关于Spring MVC：通用的DAO和服务类的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！