spring boot-jpa整合QueryDSL来简化复杂操作

前言

使用过spring data jpa的同学,都很清楚,对于复杂的sql查询,处理起来还是比较复杂的,而本文中的QueryDSL就是用来简化JPA操作的。

Querydsl定义了一种常用的静态类型语法,用于在持久域模型数据之上进行查询。JDO和JPA是Querydsl的主要集成技术。本文旨在介绍如何使用Querydsl与JPA组合使用。JPA的Querydsl是JPQL和Criteria查询的替代方法。QueryDSL仅仅是一个通用的查询框架,专注于通过Java API构建类型安全的SQL查询。

要想使用QueryDSL,需要做两个前提操作:

1、pom文件中,加入依赖


		
			com.querydsl
			querydsl-jpa
		
		
			com.querydsl
			querydsl-apt
			provided
		
2、pom文件中,加入编译插件


				com.mysema.maven
				apt-maven-plugin
				1.1.3
				
					
						
							process
						
						
							target/generated-sources/java
							com.querydsl.apt.jpa.JPAAnnotationProcessor
						
					
				
			
该插件会 查找使用javax.persistence.Entity注解的域类型,并为它们生成对应的查询类型。下面以User实体类来说明,生成的查询类型如下:

package com.chhliu.springboot.jpa.entity;

import static com.querydsl.core.types.PathMetadataFactory.*;

import com.querydsl.core.types.dsl.*;

import com.querydsl.core.types.PathMetadata;
import javax.annotation.Generated;
import com.querydsl.core.types.Path;


/**
 * QUser is a Querydsl query type for User
 */
@Generated("com.querydsl.codegen.EntitySerializer")
public class QUser extends EntityPathBase {

    private static final long serialVersionUID = 1153899872L;

    public static final QUser user = new QUser("user");

    public final StringPath address = createString("address");

    public final NumberPath age = createNumber("age", Integer.class);

    public final NumberPath id = createNumber("id", Integer.class);

    public final StringPath name = createString("name");

    public QUser(String variable) {
        super(User.class, forVariable(variable));
    }

    public QUser(Path path) {
        super(path.getType(), path.getMetadata());
    }

    public QUser(PathMetadata metadata) {
        super(User.class, metadata);
    }

}

我们建立好实体类之后,然后运行mvn clean complie命令,就会在
target/generated-sources/java
目录下生成对应的查询类型。然后将生成的类都拷贝到项目中,即可。

本文涉及到的Entity如下:

package com.chhliu.springboot.jpa.entity;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="t_user")
public class User implements Serializable{

    /**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	
	@Id()
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private String name;
    private String address;
    private int age;
	…………省略getter,setter方法…………
	/**
	 * attention:
	 * Details:方便查看测试结果
	 * @author chhliu
	 */
	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", address=" + address + ", age=" + age + "]";
	}
}
上面的这个实体类,主要用于单表操作。

package com.chhliu.springboot.jpa.entity;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

/**
 * 描述:TODO
 * @author chhliu
 */
@Entity
@Table(name="PERSON")
public class Person {
	@Id
	@GeneratedValue
	private Integer id;
	private String name;
	private String address;
	
	@OneToOne(mappedBy="person", cascade={CascadeType.PERSIST, CascadeType.REMOVE, CascadeType.MERGE})
	private IDCard idCard;
     
        …………省略getter,setter方法…………

	@Override
	public String toString() {
		return "Person [id=" + id + ", name=" + name + ", address=" + address + ", idCard=" + idCard + "]";
	}
}
package com.chhliu.springboot.jpa.entity;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

/**
 * 描述:
 * @author chhliu
 */
@Entity
@Table(name="IDCARD")
public class IDCard {
	@Id
	@GeneratedValue
	private Integer id;
	private String idNo;
	@OneToOne(cascade={CascadeType.MERGE, CascadeType.REMOVE, CascadeType.PERSIST}, fetch=FetchType.EAGER)
	private Person person;
	
       …………省略getter,setter方法…………

	@Override
	public String toString() {
		return "IDCard [id=" + id + ", idNo=" + idNo + ", person=" + person + "]";
	}
}
上面两个Entity主要用于一对一关系的示例操作

package com.chhliu.springboot.jpa.entity;

import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

/**
 * 描述:Order实体类
 * @author chhliu
 */
@Entity
@Table(name="ORDER_C")
public class Order {
	@Id
	@GeneratedValue
	@Column(name="ID")
	private Integer id;
	
	@Column(length=20, name="ORDER_NAME")
	private String orderName;
	
	@Column(name="COUNT")
	private Integer count;
	
	@OneToMany(mappedBy = "order",cascade={CascadeType.PERSIST,CascadeType.REMOVE},fetch = FetchType.EAGER)
	private List orderItems;
        
        …………省略getter,setter方法…………
}
package com.chhliu.springboot.jpa.entity;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

/**
 * 描述:OrderItem实体类
 * @author chhliu
 */
@Entity
@Table(name="ORDER_ITEM")
public class OrderItem {
	@Id
	@GeneratedValue
	@Column(name="ID", nullable=false)
	private Integer id;
	
	@Column(name="ITEM_NAME", length=20)
	private String itemName;
	
	@Column(name="PRICE")
	private Integer price;
	
	@ManyToOne(cascade={CascadeType.PERSIST,CascadeType.REMOVE, CascadeType.MERGE}, fetch=FetchType.EAGER)
    @JoinColumn(name = "ORDER_ID")
	private Order order;

        …………省略getter,setter方法…………
}
上面两个Entity用于展示一对多关系的示例操作。

首先,我们来看单表操作

1、使用spring data jpa

要想使用spring data jpa提供的QueryDSL功能,很简单,直接继承接口即可。Spring Data JPA中提供了QueryDslPredicateExecutor接口,用于支持QueryDSL的查询操作接口,如下:

package com.chhliu.springboot.jpa.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.querydsl.QueryDslPredicateExecutor;

import com.chhliu.springboot.jpa.entity.User;

public interface UserRepositoryDls extends JpaRepository, QueryDslPredicateExecutor{// 继承QueryDslPredicateExecutor接口

}
QueryDslPredicateExecutor接口提供了如下方法:

public interface QueryDslPredicateExecutor {

	T findOne(Predicate predicate);

	Iterable findAll(Predicate predicate);

	Iterable findAll(Predicate predicate, Sort sort);

	Iterable findAll(Predicate predicate, OrderSpecifier... orders);

	Iterable findAll(OrderSpecifier... orders);

	Page findAll(Predicate predicate, Pageable pageable);

	long count(Predicate predicate);

	boolean exists(Predicate predicate);
}
以上方法的使用和spring data jpa中的其他接口使用方法类似,详情请参考:

http://blog.csdn.net/liuchuanhong1/article/details/52042477

测试如下:

public User findUserByUserName(final String userName){
		/**
		 * 该例是使用spring data QueryDSL实现
		 */
		QUser quser = QUser.user;
		Predicate predicate = quser.name.eq(userName);// 根据用户名,查询user表
		return repository.findOne(predicate);
	}
对应的sql如下:

select user0_.id as id1_5_, user0_.address as address2_5_, user0_.age as age3_5_, user0_.name as name4_5_ from t_user user0_ where  user0_.name=?
单表操作示例代码如下:

package com.chhliu.springboot.jpa.repository;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import javax.transaction.Transactional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
import org.springframework.stereotype.Component;

import com.chhliu.springboot.jpa.entity.QUser;
import com.chhliu.springboot.jpa.entity.User;
import com.querydsl.core.types.Predicate;
import com.querydsl.jpa.impl.JPAQueryFactory;

/**
 * 描述:QueryDSL JPA
 * @author chhliu
 */
@Component
@Transactional
public class UserRepositoryManagerDsl {
	@Autowired
	private UserRepositoryDls repository;
	
	@Autowired
	@PersistenceContext
	private EntityManager entityManager;

        private JPAQueryFactory queryFactory;
    
     @PostConstruct
     public void init() {
        queryFactory = new JPAQueryFactory(entityManager);
     }

       public User findUserByUserName(final String userName){
	 	/**
		 * 该例是使用spring data QueryDSL实现
		 */
		QUser quser = QUser.user;
		Predicate predicate = quser.name.eq(userName);
		return repository.findOne(predicate);
	}
	
	/**
	 * attention:
	 * Details:查询user表中的所有记录
	 */
	public List findAll(){
		QUser quser = QUser.user;
		return queryFactory.selectFrom(quser)
					.fetch();
	}
	
	/**
	 * Details:单条件查询
	 */
	public User findOneByUserName(final String userName){
		QUser quser = QUser.user;
		return queryFactory.selectFrom(quser)
			.where(quser.name.eq(userName))
			.fetchOne();
	}
	
	/**
	 * Details:单表多条件查询
	 */
	public User findOneByUserNameAndAddress(final String userName, final String address){
		QUser quser = QUser.user;
		return queryFactory.select(quser)
			.from(quser) // 上面两句代码等价与selectFrom
			.where(quser.name.eq(userName).and(quser.address.eq(address)))// 这句代码等同于where(quser.name.eq(userName), quser.address.eq(address))
			.fetchOne();
	}
	
	/**
	 * Details:使用join查询
	 */
	public List findUsersByJoin(){
		QUser quser = QUser.user;
		QUser userName = new QUser("name");
		return queryFactory.selectFrom(quser)
			.innerJoin(quser)
			.on(quser.id.intValue().eq(userName.id.intValue()))
			.fetch();
	}
	
	/**
	 * Details:将查询结果排序
	 */
	public List findUserAndOrder(){
		QUser quser = QUser.user;
		return queryFactory.selectFrom(quser)
			.orderBy(quser.id.desc())
			.fetch();
	}
	
	/**
	 * Details:Group By使用
	 */
	public List findUserByGroup(){
		QUser quser = QUser.user;
		return queryFactory.select(quser.name)
					.from(quser)
					.groupBy(quser.name)
					.fetch();
	}
	
	/**
	 * Details:删除用户
	 */
	public long deleteUser(String userName){
		QUser quser = QUser.user;
		return queryFactory.delete(quser).where(quser.name.eq(userName)).execute();
	}
	
	/**
	 * Details:更新记录
	 */
	public long updateUser(final User u, final String userName){
		QUser quser = QUser.user;
		return queryFactory.update(quser).where(quser.name.eq(userName))
			.set(quser.name, u.getName())
			.set(quser.age, u.getAge())
			.set(quser.address, u.getAddress())
			.execute();
	}
	
	/**
	 * Details:使用原生Query
	 */
	public User findOneUserByOriginalSql(final String userName){
		QUser quser = QUser.user;
		Query query = queryFactory.selectFrom(quser)
				.where(quser.name.eq(userName)).createQuery();
		return (User) query.getSingleResult();
	}
	
	/**
	 * Details:分页查询单表
	 */
	public Page findAllAndPager(final int offset, final int pageSize){
		Predicate predicate = QUser.user.id.lt(10);
		Sort sort = new Sort(new Sort.Order(Sort.Direction.DESC, "id"));
		PageRequest pr = new PageRequest(offset, pageSize, sort);
		return repository.findAll(predicate, pr);
	}
}
多表操作示例(一对一)如下:

package com.chhliu.springboot.jpa.repository;

import java.util.ArrayList;
import java.util.List;

import javax.annotation.PostConstruct;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

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

import com.chhliu.springboot.jpa.dto.PersonIDCardDto;
import com.chhliu.springboot.jpa.entity.QIDCard;
import com.chhliu.springboot.jpa.entity.QPerson;
import com.querydsl.core.QueryResults;
import com.querydsl.core.Tuple;
import com.querydsl.core.types.Predicate;
import com.querydsl.jpa.impl.JPAQuery;
import com.querydsl.jpa.impl.JPAQueryFactory;

@Component
public class PersonAndIDCardManager {
    @Autowired
    @PersistenceContext
    private EntityManager entityManager;
    
    private JPAQueryFactory queryFactory;
    
    @PostConstruct
    public void init() {
        queryFactory = new JPAQueryFactory(entityManager);
    }
    
    /**
     * Details:多表动态查询
     */
    public List findAllPersonAndIdCard(){
        Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());
        JPAQuery jpaQuery = queryFactory.select(QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name)
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate);
        return jpaQuery.fetch();
    }
    
    /**
     * Details:将查询结果以DTO的方式输出
     */
    public List findByDTO(){
        Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());
        JPAQuery jpaQuery = queryFactory.select(QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name)
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate);
        List tuples = jpaQuery.fetch();
        List dtos = new ArrayList();
        if(null != tuples && !tuples.isEmpty()){
            for(Tuple tuple:tuples){
                String address = tuple.get(QPerson.person.address);
                String name = tuple.get(QPerson.person.name);
                String idCard = tuple.get(QIDCard.iDCard.idNo);
                PersonIDCardDto dto = new PersonIDCardDto();
                dto.setAddress(address);
                dto.setIdNo(idCard);
                dto.setName(name);
                dtos.add(dto);
            }
        }
        return dtos;
    }
    
    /**
     * Details:多表动态查询,并分页
     */
    public QueryResults findByDtoAndPager(int offset, int pageSize){
        Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());
        return queryFactory.select(QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name)
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate)
                .offset(offset)
                .limit(pageSize)
                .fetchResults();
    }
}

上面将查询结果以DTO的方式输出的示例中,在查询结束后,将查询结果手动的转换成了DTO对象,这种方式其实不太优雅,QueryDSL给我们提供了更好的方式,见下面的示例:

/**
     * Details:方式一:使用Bean投影
     */
    public List findByDTOUseBean(){
        Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());
        return queryFactory.select(
                Projections.bean(PersonIDCardDto.class, QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name))
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate)
                .fetch();
    }
    
    /**
     * Details:方式二:使用fields来代替setter
     */
    public List findByDTOUseFields(){
        Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());
        return queryFactory.select(
                Projections.fields(PersonIDCardDto.class, QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name))
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate)
                .fetch();
    }
    
    /**
     * Details:方式三:使用构造方法,注意构造方法中属性的顺序必须和构造器中的顺序一致
     */
    public List findByDTOUseConstructor(){
        Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());
        return queryFactory.select(
                Projections.constructor(PersonIDCardDto.class, QPerson.person.name, QPerson.person.address, QIDCard.iDCard.idNo))
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate)
                .fetch();
    }
上面只是提供了几种思路,当然,还可以使用@QueryProjection来实现,非常灵活。
一对多示例:
package com.chhliu.springboot.jpa.repository;

import java.util.List;

import javax.annotation.PostConstruct;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

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

import com.chhliu.springboot.jpa.entity.QOrder;
import com.chhliu.springboot.jpa.entity.QOrderItem;
import com.querydsl.core.Tuple;
import com.querydsl.core.types.Predicate;
import com.querydsl.jpa.impl.JPAQuery;
import com.querydsl.jpa.impl.JPAQueryFactory;

@Component
public class OrderAndOrderItemManager {
    
    @Autowired
    @PersistenceContext
    private EntityManager entityManager;
    
    private JPAQueryFactory queryFactory;
    
    @PostConstruct
    public void init() {
        queryFactory = new JPAQueryFactory(entityManager);
    }
    
    /**
     * Details:一对多,条件查询
     */
    public List findOrderAndOrderItemByOrderName(String orderName){
        //添加查询条件
        Predicate predicate = QOrder.order.orderName.eq(orderName);
        JPAQuery jpaQuery = queryFactory.select(QOrder.order, QOrderItem.orderItem)
                                        .from(QOrder.order, QOrderItem.orderItem)
                                        .where(QOrderItem.orderItem.order.id.intValue().eq(QOrder.order.id.intValue()), predicate);
        
        //拿到结果
        return jpaQuery.fetch();
    }
    
    /**
     * Details:多表连接查询
     */
    public List findAllByOrderName(String orderName){
        //添加查询条件
        Predicate predicate = QOrder.order.orderName.eq(orderName);
        JPAQuery jpaQuery = queryFactory.select(QOrder.order, QOrderItem.orderItem)
                                        .from(QOrder.order, QOrderItem.orderItem)
                                        .rightJoin(QOrder.order)
                                        .on(QOrderItem.orderItem.order.id.intValue().eq(QOrder.order.id.intValue()));
        jpaQuery.where(predicate);
        //拿到结果
        return jpaQuery.fetch();
    }
}

从上面的示例中,我们可以看出,QueryDSL大大的简化了我们的操作

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