23. Spring Boot JPA BaseDao 配置 文章

 参考文献：（早期JPA版本的描述）

https://blog.csdn.net/yingxiake/article/details/51017797

https://www.jianshu.com/p/73f48095a7bf

https://www.cnblogs.com/ityouknow/p/5891443.html

https://www.jianshu.com/p/da4f584d6e14 

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

spring:
  datasource:
    jpa:
        show-sql: true #控制台显示SQL
        hibernate:
           ddl-auto: update #更新或创建表

package com.example.jdbc.model;

import javax.persistence.*;

@Entity
public class User {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Integer id;

    @Column
    private String name;

    @Column
    private Integer age;

    @Column
    private Integer sex;

    get() set()......
}

package com.example.jdbc.dao;

import com.example.jdbc.model.User;
import org.springframework.data.jpa.repository.JpaRepository;

public interface UserDao extends JpaRepository<User,Integer> {

}

自己拓展JPA，不光定义接口，还要有实现类和自定义的方法（名称随意起） 

package com.example.jdbc.dao;

/**
 * Created with IDEA
 * author:Guchunchao
 * Date:2018/12/3
 * Time:下午6:02
 */

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.repository.NoRepositoryBean;

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


@NoRepositoryBean
public interface BaseDao<T,ID extends Serializable> extends JpaRepository<T,ID>, JpaSpecificationExecutor<T> {

    public List<Object[]> selectBySQL(String sql);

}

package com.example.jdbc.dao;

/**
 * Created with IDEA
 * author:Guchunchao
 * Date:2018/12/3
 * Time:下午6:03
 */
import org.springframework.data.jpa.repository.support.JpaEntityInformation;
import org.springframework.data.jpa.repository.support.JpaEntityInformationSupport;
import org.springframework.data.jpa.repository.support.SimpleJpaRepository;

import javax.persistence.EntityManager;
import java.io.Serializable;
import java.util.List;

/**
 * 解决方法
 * This is a bug in IntelliJ that is fixed in 13.1. http://youtrack.jetbrains.com/issue/IDEA-120977
 * Class doesn't contain matching constructor for autowiring
 */
public class BaseDaoImpl<T, ID extends Serializable> extends SimpleJpaRepository<T,ID>
        implements BaseDao<T,ID> {

    private EntityManager entityManager;


    public BaseDaoImpl(JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager) {
        super(entityInformation, entityManager);
    }


    //父类没有不带参数的构造方法，这里手动构造父类
    public BaseDaoImpl(Class<T> domainClass, EntityManager entityManager) {
        this(JpaEntityInformationSupport.getEntityInformation(domainClass, entityManager), entityManager);
        this.entityManager = entityManager;
    }

    //通过EntityManager来完成自定义的查询
    @Override
    public List<Object[]> selectBySQL(String sql) {
        return entityManager.createNativeQuery(sql).getResultList();
    }
}

package com.example.jdbc.dao;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.support.JpaRepositoryFactory;
import org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean;
import org.springframework.data.jpa.repository.support.JpaRepositoryImplementation;
import org.springframework.data.repository.core.RepositoryInformation;
import org.springframework.data.repository.core.RepositoryMetadata;
import org.springframework.data.repository.core.support.RepositoryFactorySupport;

import javax.persistence.EntityManager;
import java.io.Serializable;

public class BaseDaoFactoryBean<R extends JpaRepository<T, ID>, T,
        ID extends Serializable> extends JpaRepositoryFactoryBean<R, T, ID> {

    public BaseDaoFactoryBean(Class<? extends R> repositoryInterface) {
        super(repositoryInterface);
    }

    @Override
    protected RepositoryFactorySupport createRepositoryFactory(EntityManager em) {
        return new BaseDaoFactory(em);
    }

    //创建一个内部类，该类不用在外部访问
    private static class BaseDaoFactory<T, I extends Serializable>
            extends JpaRepositoryFactory {

        private final EntityManager em;

        public BaseDaoFactory(EntityManager em) {
            super(em);
            this.em = em;
        }

        //此方法以经在父类方法中实现了,所以不用再自定义了
//        @Override
//        protected JpaRepositoryImplementation getTargetRepository(RepositoryInformation information) {
//            return super(information, em);
//        }

        //设置具体的实现类的class
        @Override
        protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {
            return BaseDaoImpl.class;
        }
    }

}

package com.example.jdbc;

import com.example.jdbc.dao.BaseDaoFactoryBean;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@EnableJpaRepositories(repositoryFactoryBeanClass = BaseDaoFactoryBean.class, basePackages ="com.example.jdbc.dao")
@EnableTransactionManagement
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
public class SpringBootJdbcApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootJdbcApplication.class, args);
    }
}

注意：这是SpringBoot 2.1.1版本集成的JPA的实现，与上面的引用文章内容有出入。早起版本请参见引用文章