QueryDSL学习笔记
归和惬
QueryDSL简介
- 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。
- Querydsl可以通过一组通用的查询API为用户构建出适合不同类型ORM框架或者是SQL的查询语句，也就是说QueryDSL是基于各种ORM框架以及SQL之上的一个通用的查询框架。
- 借助QueryDSL可以在任何支持的ORM框架或者SQL平台上以一种通用的API方式来构建查询。目前QueryDSL支持的平台包括JPA,JDO,SQL,Java
Collections,RDF,Lucene,Hibernate Search。
使用QueryDSL需先通过Maven插件编译自动生成实体类型的结构查询实体。
mvn clean complie
package com.ly.domain;
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;
/**
* QBank is a Querydsl query type for Bank
*/
@Generated("com.querydsl.codegen.EntitySerializer")
public class QBank extends EntityPathBase<Bank> {
private static final long serialVersionUID = -1720494478L;
public static final QBank bank = new QBank("bank");
public final StringPath bankType = createString("bankType");
public final DateTimePath<java.util.Date> gmtCreate = createDateTime("gmtCreate", java.util.Date.class);
public final DateTimePath<java.util.Date> gmtModified = createDateTime("gmtModified", java.util.Date.class);
public final NumberPath<Long> id = createNumber("id", Long.class);
public final NumberPath<Long> isDeleted = createNumber("isDeleted", Long.class);
public final StringPath name = createString("name");
public final NumberPath<Long> ordernum = createNumber("ordernum", Long.class);
public QBank(String variable) {
super(Bank.class, forVariable(variable));
}
public QBank(Path<? extends Bank> path) {
super(path.getType(), path.getMetadata());
}
public QBank(PathMetadata metadata) {
super(Bank.class, metadata);
}
}
使用范例
单表查询
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<User> 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<User> 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<User> findUserAndOrder(){
QUser quser = QUser.user;
return queryFactory.selectFrom(quser)
.orderBy(quser.id.desc())
.fetch();
}
/**
* Details：Group By使用
*/
public List<String> 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<User> 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)
/**
* Details：多表动态查询
*/
public List<Tuple> findAllPersonAndIdCard(){
Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());
JPAQuery<Tuple> 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<PersonIDCardDto> findByDTO(){
Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());
JPAQuery<Tuple> jpaQuery = queryFactory.select(QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name)
.from(QIDCard.iDCard, QPerson.person)
.where(predicate);
List<Tuple> tuples = jpaQuery.fetch();
List<PersonIDCardDto> dtos = new ArrayList<PersonIDCardDto>();
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<Tuple> 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();
}
/**
* Details：方式一：使用Bean投影
*/
public List<PersonIDCardDto> 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<PersonIDCardDto> 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<PersonIDCardDto> 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();
}
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