springboot的jpa可以根據方法名自動解析sql 非常方便, 只需要在 dao介面中定義方法即可;

下面是一個 demo

package com.bus365.root.dao;


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

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;

import com.bus365.root.model.User;

public interface UserDao extends JpaRepository<User,Long>,JpaSpecificationExecutor<User>,Serializable {

	User findByName(String name);

	User findByNameAndAge(String name, Integer age);

	User findByNameOrAge(String name, Integer age);

	
	/*@Query(value = "from User where name = :name")
	List<User> findbyname(@Param("name") String name);*/
}
 

下面展示service層呼叫:

@Override
	public User findByName(String name) {
		User user = userDao.findByName(name);
		return user;
	}

	@Override
	public User findByNameAndAge(String name, Integer age) {
		User user = userDao.findByNameAndAge(name,age);
		return user;
	}

	@Override
	public User findByNameOrAge(String name, Integer age) {
		User user = userDao.findByNameOrAge(name,age);
		return user;
	}
 

具體的關鍵字，使用方法和生產成SQL如下表所示

下面介紹使用java原生的jpa操作資料庫,對jpa熟悉的朋友應該很快就能理解,springboot使用原生jpa的關鍵是引入entitymanger

看一下service層

package com.bus365.root.service.impl;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.stereotype.Service;

import com.bus365.root.model.Address;
import com.bus365.root.service.AddressService;

@Service
public class AddressServiceImpl implements AddressService {

	@PersistenceContext
	private EntityManager entityManager;
	
	public List<Address> listAddress(){
		List resultList = entityManager.createNativeQuery("select * from address ", Address.class).getResultList();
		return resultList;
	}
}

注意 @PersistenceContext
    private EntityManager entityManager;
    動態引入entitymanger , 之後就能正常使用了;

    createNativeQuery是操作原生mysql方法;支援跨表查詢;

jpa的事務 直接使用註解Transactional 引數rollbackon表示回滾條件, 這個註解一搬加在service層;  注意getSingleResult 如果查不到資料會報錯;

@Transactional(rollbackOn= {Exception.class})
	public Address getAddressByid(Long id) {
		Address singleResult = null;
		try {
			singleResult = (Address) entityManager
					.createNativeQuery("select * from address where id = :id", Address.class).setParameter("id", id)
					.getSingleResult();
		} catch (Exception e) {
			e.printStackTrace();
		}
		return singleResult;
	}

jpa實現多表聯查;

@Transactional
	public List<Object[]> getUserWithAddrByid(Long id) {
		List resultList = entityManager.createNativeQuery(
				"select u.id id,u.age age,u.name name,a.name aname,a.completeaddress addre from user u left join address a on u.addressid = a.id where u.id = :id")
				.setParameter("id", id).getResultList();
		return resultList;
	}

      這是一個聯查user 和address的例子, 返回的結果是個List<Object[]> 專案中一般封裝成vo 類,或者List<Map<String,Object>> 的形式