spring-data-jpa -hibernate --specificationExecutor

Specifications动态查询

在查询某个实体的时候，给定的条件是不固定的，这时就需要动态构建相应的查询语句，在Spring Data JPA中可以通过JpaSpecificationExecutor接口查询。相比JPQL,其优势是类型安全,更加的面向对象

import java.util.List;
 
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
 
/**
 *    JpaSpecificationExecutor中定义的方法
 **/
 public interface JpaSpecificationExecutor<T> {
       //根据条件查询一个对象
     T findOne(Specification<T> spec);
       //根据条件查询集合
     List<T> findAll(Specification<T> spec);
       //根据条件分页查询
     Page<T> findAll(Specification<T> spec, Pageable pageable);
       //排序查询查询
     List<T> findAll(Specification<T> spec, Sort sort);
       //统计查询
     long count(Specification<T> spec);
}

对于JpaSpecificationExecutor，这个接口基本是围绕着Specification接口来定义的。可以简单的理解为，Specification构造的就是查询条件。

 //构造查询条件
    /**
    *    root    ：Root接口，代表查询的根对象，可以通过root获取实体中的属性
    *    query    ：代表一个顶层查询对象，用来自定义查询
    *    cb        ：用来构建查询，此对象里有很多条件方法
    **/
    public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb);

配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:jpa="http://www.springframework.org/schema/data/jpa"
       xmlns:task="http://www.springframework.org/schema/task"
       xmlns:contxt="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/data/jpa
        http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">
 
    <!-- 配置实体类管理工厂 -->
    <bean id="entityManagerFactoryBean" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource"/>
 
        <property name="packagesToScan" value="com.ytfs.entity"/>
        <property name="persistenceProvider">
            <bean class="org.hibernate.jpa.HibernatePersistenceProvider"/>
        </property>
 
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <property name="showSql" value="true"/>
                <property name="database" value="MYSQL"/>
                <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect"/>
                <property name="generateDdl" value="false"/>
            </bean>
        </property>
    </bean>
 
    <!-- 配置事务管理器 -->
 
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="dataSource" ref="dataSource"/>
    </bean>
 
    <!-- 整合jpa -->
    <jpa:repositories base-package="com.ytfs.dao" transaction-manager-ref="transactionManager"
                      entity-manager-factory-ref="entityManagerFactoryBean"/>
 
    <!-- spring的包扫描 -->
 
    <context:component-scan base-package="com.ytfs"/>
    <!-- 整合数据源 -->
    <context:property-placeholder location="classpath:jdbcConfig.properties"/>
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
        <property name="url" value="${jdbc.url}"/>
    </bean>
</beans>

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/jpa
jdbc.username=root
jdbc.password=root

实体类

　　

package com.ytfs.entity;
 
import javax.persistence.*;
import java.io.Serializable;
 
/**
 * @Classname Customer
 * @Description TODO(客户的实体类)
 * @Date 2020/5/6 16:15
 * @Created by ytfs
 */
 
@Entity
@Table(name = "cst_customer")
public class Customer implements Serializable {
    /**
     * cust_id` bigint(32) NOT NULL AUTO_INCREMENT COMMENT '客户编号(主键)',
     * `cust_name` varchar(32) NOT NULL COMMENT '客户名称(公司名称)',
     * `cust_source` varchar(32) DEFAULT NULL COMMENT '客户信息来源',
     * `cust_industry` varchar(32) DEFAULT NULL COMMENT '客户所属行业',
     * `cust_level` varchar(32) DEFAULT NULL COMMENT '客户级别',
     * `cust_address` varchar(128) DEFAULT NULL COMMENT '客户联系地址',
     * `cust_phone` v
     */
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "cust_id")
    private Long custId;
 
    @Column(name = "cust_name")
    private String custName;
 
    @Column(name = "cust_source")
    private String custSource;
 
    @Column(name = "cust_industry")
    private String custIndustry;
 
    @Column(name = "cust_level")
    private String custLevel;
 
    @Column(name = "cust_address")
    private String custAddress;
 
    @Column(name = "cust_phone")
    private String custPhone;
 
    public Long getCustId() {
        return custId;
    }
 
    public void setCustId(Long custId) {
        this.custId = custId;
    }
 
    public String getCustName() {
        return custName;
    }
 
    public void setCustName(String custName) {
        this.custName = custName;
    }
 
    public String getCustSource() {
        return custSource;
    }
 
    public void setCustSource(String custSource) {
        this.custSource = custSource;
    }
 
    public String getCustIndustry() {
        return custIndustry;
    }
 
    public void setCustIndustry(String custIndustry) {
        this.custIndustry = custIndustry;
    }
 
    public String getCustLevel() {
        return custLevel;
    }
 
    public void setCustLevel(String custLevel) {
        this.custLevel = custLevel;
    }
 
    public String getCustAddress() {
        return custAddress;
    }
 
    public void setCustAddress(String custAddress) {
        this.custAddress = custAddress;
    }
 
    public String getCustPhone() {
        return custPhone;
    }
 
    public void setCustPhone(String custPhone) {
        this.custPhone = custPhone;
    }
 
    @Override
    public String toString() {
        return "Customer{" +
                "custId=" + custId +
                ", custName='" + custName + '\'' +
                ", custSource='" + custSource + '\'' +
                ", custIndustry='" + custIndustry + '\'' +
                ", custLevel='" + custLevel + '\'' +
                ", custAddress='" + custAddress + '\'' +
                ", custPhone='" + custPhone + '\'' +
                '}';
    }
}

Dao接口

package com.ytfs.dao;
 
import com.ytfs.entity.Customer;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
 
/**
 * @Classname ICustomerDao
 * @Description TODO(客户的数据访问层)
 * @Date 2020/5/6 16:20
 * @Created by ytfs
 */
 
public interface ICustomerDao  extends JpaRepository<Customer,Long>, JpaSpecificationExecutor<Customer> {
}

查询测试

package com.ytfs.test;
 
import com.ytfs.dao.ICustomerDao;
import com.ytfs.entity.Customer;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
import javax.persistence.criteria.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
 
/**
 * @Classname Test
 * @Description TODO(测试)
 * @Date 2020/5/6 16:21
 * @Created by ytfs
 */
 
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class TestSpringDataJPA {
 
    @Autowired
    private ICustomerDao customerDao;
 
    /**
     * 根据名称查询用户
     */
    @Test
    public void testFindAll() {
        //匿名内部类
        /**
         * 自定义查询条件
         *      1.实现Specification接口（提供泛型：查询的对象类型）
         *      2.实现toPredicate方法（构造查询条件）
         *      3.需要借助方法参数中的两个参数（
         *          root：获取需要查询的对象属性
         *          CriteriaBuilder：构造查询条件的，内部封装了很多的查询条件（模糊匹配，精准匹配）
         *       ）
         *  案例：根据客户名称查询，查询客户名为传智播客的客户
         *          查询条件
         *              1.查询方式
         *                  criteriaBuilder对象
         *              2.比较的属性名称
         *                  root对象
         *
         */
        Specification<Customer> spec = new Specification<Customer>() {
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //1.获取比较的属性
                Path<Object> custName = root.get("custName");
                //2.构造查询条件  ：    select * from cst_customer where cust_name = '传智播客'
                /**
                 * 第一个参数：需要比较的属性（path对象）
                 * 第二个参数：当前需要比较的取值
                 */
                Predicate predicate = criteriaBuilder.equal(custName, "雨听风说");//进行精准的匹配  （比较的属性，比较的属性的取值）
 
                return predicate;
            }
        };
 
        List<Customer> customers = this.customerDao.findAll(spec);
 
        customers.forEach(System.out::println);
    }
 
    /**
     * 多条件查询
     */
 
    @Test
    public void testFindOne() {
        /**
         *  root:获取属性
         *      客户名
         *      id
         *  criteriaBuilder：构造查询
         *      1.构造客户名的精准匹配查询
         *      2.构造所属行业的精准匹配查询
         *      3.将以上两个查询联系起来
         */
        Specification<Customer> spec = new Specification<Customer>() {
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
 
                Path<Object> path = root.get("custName");
 
                Path<Object> path1 = root.get("custId");
                /*
                构造查询
                 */
                //1.构造客户名的精准匹配查询
                Predicate predicate = criteriaBuilder.equal(path, "雨听风说");//第一个参数，path（属性），第二个参数，属性的取值
                //2..构造id的精准匹配查询
                Predicate equal = criteriaBuilder.equal(path1, 1L);
 
                //3.将多个查询条件组合到一起：组合（满足条件一并且满足条件二：与关系，满足条件一或满足条件二即可：或关系）
                // criteriaBuilder.or();//以或的形式拼接多个查询条件
                Predicate predicate1 = criteriaBuilder.and(predicate, equal);//以与的形式将条件拼接在一起
                return predicate1;
            }
        };
 
        Optional<Customer> customers = this.customerDao.findOne(spec);
 
        customers.stream().forEach(c -> {
            System.out.println("c = " + c);
        });
    }
 
    /**
     * 案例：完成根据客户名称的模糊匹配，返回客户列表
     *      客户名称包含 ’听风‘
     *
     * equal ：直接的到path对象（属性），然后进行比较即可
     * gt，lt,ge,le,like : 得到path对象，根据path指定比较的参数类型，再去进行比较
     *      指定参数类型：path.as(类型的字节码对象)
     */
     @Test
     public void testLike() {
 
         Specification<Customer> spec = new Specification<Customer>() {
             @Override
             public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
 
                 Path<Object> custName = root.get("custName");
 
                 Predicate predicate = criteriaBuilder.like(custName.as(String.class), "%雨听%");
 
                 return predicate;
             }
         };
 
         List<Customer> customers = this.customerDao.findAll(spec);
 
         customers.forEach(System.out::println);
 
     }
 
    /**
     * 查询并排序
     */
 
    @Test
    public void testLikeAndSort() {
 
        Specification<Customer> spec = new Specification<Customer>() {
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
 
                Path<Object> custName = root.get("custName");
 
                Predicate predicate = criteriaBuilder.like(custName.as(String.class), "%雨听%");
 
                return predicate;
            }
        };
        //添加排序
        //创建排序对象,需要调用构造方法实例化sort对象
        //第一个参数：排序的顺序（倒序，正序）
        //   Sort.by("custId").descending():倒序
        //    Sort.by("custId").ascending(); ： 升序
        //第二个参数：排序的属性名称
 
        Sort sort = Sort.by("custId").descending();
        List<Customer> customers = this.customerDao.findAll(spec,sort);
 
        customers.forEach(System.out::println);
    }
 
    /**
     * 分页查询
     *      Specification: 查询条件
     *      Pageable：分页参数
     *          分页参数：查询的页码，每页查询的条数
     *          findAll(Specification,Pageable)：带有条件的分页
     *          findAll(Pageable)：没有条件的分页
     *  返回：Page（springDataJpa为我们封装好的pageBean对象，数据列表，共条数）
     */
     @Test
     public void testPage() {
 
         //PageRequest对象是Pageable接口的实现类
         /**
          * 创建PageRequest的过程中，需要调用他的构造方法传入两个参数
          *      第一个参数：当前查询的页数（从0开始）
          *      第二个参数：每页查询的数量
          */
         Pageable pageable = PageRequest.of(0,2);
 
         Page<Customer> page = this.customerDao.findAll(pageable);
 
         System.out.println(page.getContent()); //得到数据集合列表
         System.out.println(page.getTotalElements());//得到总条数
         System.out.println(page.getTotalPages());//得到总页数
 
     }
}