Querydsl 简单语句格式

    com.querydsl
    querydsl-jpa


    com.querydsl
    querydsl-apt




    
        
        
            com.mysema.maven
            apt-maven-plugin
            1.1.3
            
                
                    
                        process
                    
                    
                        target/generated-sources/java
                        com.querydsl.apt.jpa.JPAAnnotationProcessor
                    
                
            
        
        
            org.springframework.boot
            spring-boot-maven-plugin
        
    

 

 进行注入 EntityManager   和 事物管理:

@SpringBootApplication
public class DemoApplication extends SpringBootServletInitializer {
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(DemoApplication.class);
    }


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

    @Bean
    public JPAQueryFactory jpaQueryFactory(EntityManager entityManager) {
        return new JPAQueryFactory(entityManager);
    }

    @Bean
    public PlatformTransactionManager transactionManager(DataSource dataSource) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setDataSource(dataSource);
        return transactionManager;
    }

}

# 子查询

QDepartment department = QDepartment.department;
QDepartment d = new QDepartment("d");
queryFactory.selectFrom(department)
    .where(department.size.eq(
        JPAExpressions.select(d.size.max()).from(d)))
     .fetch();


QEmployee employee = QEmployee.employee;
QEmployee e = new QEmployee("e");
queryFactory.selectFrom(employee)
    .where(employee.weeklyhours.gt(
        JPAExpressions.select(e.weeklyhours.avg())
            .from(employee.department.employees, e)
            .where(e.manager.eq(employee.manager))))
    .fetch();



# 更新修改

QCustomer customer = QCustomer.customer;
queryFactory.update(customer)
    .set(customer.name, "Bobby")
    .where(customer.name.eq("Bob"))
    .execute();

queryFactory.update(customer)
    .setNull(customer.name)
    .where(customer.name.eq("Bob"))
    .execute();



# 删除

QCustomer customer = QCustomer.customer;
queryFactory.delete(customer).execute();
queryFactory.delete(customer).where(customer.level.lt(3)).execute();



# 返回为 Tuple 类型的对象取值

# 1.
public List getOrdersListOnlinePaymentUnmatch() {
        QOrders qOrders = QOrders.orders;
        return hibernateQueryFactory
                .select(qOrders.ordersSn, qOrders.ordersAmount, qOrders.storeDiscountAmount, qOrders.couponAmount, qOrders.paymentTime)
                .from(qOrders)
                .fetch();
    }

# 2.
List orders = ordersDao.getOrdersListOnlinePaymentUnmatch();

# 3.获取第1个参数
orders.get(i).get(0, Long.class)

DTO

query = new JPASQLQuery(entityManager, templates);
List catDTOs = query.select(Projections.constructor(CatDTO.class, cat.id, cat.name))
    .from(cat)
    .orderBy(cat.name.asc())
    .fetch();


public ServiceResponse