<Spring Data JPA>二 Spring Data Jpa

1.pom依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>spring-data-jpa</artifactId>
        <groupId>org.maple</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>jpa-02</artifactId>

    <properties>
        <spring.version>5.0.2.RELEASE</spring.version>
        <hibernate.version>5.0.7.Final</hibernate.version>
        <slf4j.version>1.6.6</slf4j.version>
        <log4j.version>1.2.12</log4j.version>
        <c3p0.version>0.9.1.2</c3p0.version>
        <mysql.version>5.1.6</mysql.version>
    </properties>

    <dependencies>
        <!-- junit单元测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

        <!-- spring beg -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.6.8</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- spring对orm框架的支持包-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- spring end -->

        <!-- hibernate beg -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>${hibernate.version}</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>${hibernate.version}</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>5.2.1.Final</version>
        </dependency>
        <!-- hibernate end -->

        <!-- c3p0 beg -->
        <dependency>
            <groupId>c3p0</groupId>
            <artifactId>c3p0</artifactId>
            <version>${c3p0.version}</version>
        </dependency>
        <!-- c3p0 end -->

        <!-- log end -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>${log4j.version}</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
        <!-- log end -->


        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>${mysql.version}</version>
        </dependency>

        <!-- spring data jpa 的坐标-->
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
            <version>1.9.0.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- el beg 使用spring data jpa 必须引入 -->
        <dependency>
            <groupId>javax.el</groupId>
            <artifactId>javax.el-api</artifactId>
            <version>2.2.4</version>
        </dependency>

        <dependency>
            <groupId>org.glassfish.web</groupId>
            <artifactId>javax.el</artifactId>
            <version>2.2.4</version>
        </dependency>
        <!-- el end -->

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.4</version>
        </dependency>
    </dependencies>

</project>

2.spring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"
       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">

    <!--spring 和 spring data jpa的配置-->

    <!-- 1.创建entityManagerFactory对象交给spring容器管理-->
    <bean id="entityManagerFactoty" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <!--配置的扫描的包（实体类所在的包） -->
        <property name="packagesToScan" value="org.maple.domain" />
        <!-- jpa的实现厂家 -->
        <property name="persistenceProvider">
            <bean class="org.hibernate.jpa.HibernatePersistenceProvider"/>
        </property>

        <!--jpa的供应商适配器 -->
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <!--配置是否自动创建数据库表 -->
                <property name="generateDdl" value="false" />
                <!--指定数据库类型 -->
                <property name="database" value="MYSQL" />
                <!--数据库方言：支持的特有语法 -->
                <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect" />
                <!--是否显示sql -->
                <property name="showSql" value="true" />
            </bean>
        </property>

        <!--jpa的方言 ：高级的特性 -->
        <property name="jpaDialect" >
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
        </property>

    </bean>

    <!--2.创建数据库连接池 -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="user" value="root"></property>
        <property name="password" value="root"></property>
        <property name="jdbcUrl" value="jdbc:mysql:///jpa" ></property>
        <property name="driverClass" value="com.mysql.jdbc.Driver"></property>
    </bean>

    <!--3.整合spring dataJpa-->
    <jpa:repositories base-package="org.maple.dao" transaction-manager-ref="transactionManager"
                   entity-manager-factory-ref="entityManagerFactoty" ></jpa:repositories>

    <!--4.配置事务管理器 -->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactoty"></property>
    </bean>

    <!-- 4.txAdvice-->
    <tx:advice id="txAdvice" transaction-manager="transactionManager">
        <tx:attributes>
            <tx:method name="save*" propagation="REQUIRED"/>
            <tx:method name="insert*" propagation="REQUIRED"/>
            <tx:method name="update*" propagation="REQUIRED"/>
            <tx:method name="delete*" propagation="REQUIRED"/>
            <tx:method name="get*" read-only="true"/>
            <tx:method name="find*" read-only="true"/>
            <tx:method name="*" propagation="REQUIRED"/>
        </tx:attributes>
    </tx:advice>

    <!-- 5.aop-->
    <aop:config>
        <aop:pointcut id="pointcut" expression="execution(* org.maple.service.*.*(..))" />
        <aop:advisor advice-ref="txAdvice" pointcut-ref="pointcut" />
    </aop:config>


    <!--5.声明式事务 -->

    <!-- 6. 配置包扫描-->
    <context:component-scan base-package="org.maple" ></context:component-scan>
</beans>

3.实体类

package org.maple.domain;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import lombok.experimental.Accessors;

import javax.persistence.*;

/**
 * @author mapleins
 * @Date 2019-01-10 20:31
 * @Desc
 **/
@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Accessors(chain = true)
@Entity
@Table(name = "cst_customer")
public class Customer {

    /**
     * @Id：声明主键的配置
     * @GeneratedValue:配置主键的生成策略
     *      strategy
     *          GenerationType.IDENTITY ：自增，mysql
     *                 * 底层数据库必须支持自动增长（底层数据库支持的自动增长方式，对id自增）
     *          GenerationType.SEQUENCE : 序列，oracle
     *                  * 底层数据库必须支持序列
     *          GenerationType.TABLE : jpa提供的一种机制，通过一张数据库表的形式帮助我们完成主键自增
     *          GenerationType.AUTO ： 由程序自动的帮助我们选择主键生成策略
     * @Column:配置属性和字段的映射关系
     *      name：数据库表中字段的名称
     */
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "cust_id")
    private Long custId; //客户的主键

    @Column(name = "cust_name")
    private String custName;//客户名称

    @Column(name="cust_source")
    private String custSource;//客户来源

    @Column(name="cust_level")
    private String custLevel;//客户级别

    @Column(name="cust_industry")
    private String custIndustry;//客户所属行业

    @Column(name="cust_phone")
    private String custPhone;//客户的联系方式

    @Column(name="cust_address")
    private String custAddress;//客户地址
}

4.dao接口

package org.maple.dao;

import org.maple.domain.Customer;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

/**
 * @author mapleins
 * @Date 2019-01-10 21:20
 * @Desc
 **/
/**
 * 符合SpringDataJpa的dao层接口规范
 *      JpaRepository<操作的实体类类型，实体类中主键属性的类型>
 *          * 封装了基本CRUD操作
 *      JpaSpecificationExecutor<操作的实体类类型>
 *          * 封装了复杂查询（分页）
 */
public interface CustomerDao extends JpaRepository<Customer,Long>, JpaSpecificationExecutor<Customer> {

}

5.测试（CRUD）

package org.maple.test;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.maple.dao.CustomerDao;
import org.maple.domain.Customer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

/**
 * @author mapleins
 * @Date 2019-01-10 21:22
 * @Desc
 **/
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class CustomerDaoTest {

    @Autowired
    private CustomerDao dao;

    /**
     * 查询一个 findOne 根据主键查询
     * em.find()           :立即加载
     */
    @Test
    public void findOne(){
        Customer one = dao.findOne(3l);
        System.out.println(one);
    }

    /**
     * 根据id从数据库查询
     *      @Transactional : 保证getOne正常运行
     *  getOne：
     *      em.getReference     :延迟加载
     *      * 返回的是一个客户的动态代理对象
     *      * 什么时候用，什么时候查询
     */
    @Test
    @Transactional
    public void  testGetOne() {
        Customer customer = dao.getOne(3l);
        System.out.println(customer);
    }

    /**
     * save : 保存或者更新
     *      根据传递的对象是否存在主键id，
     *      如果没有id主键属性：保存
     *      存在id主键属性，根据id查询数据，更新数据
     */
    @Test
    public void testSave() {
        Customer customer  = new Customer();
        customer.setCustName("hasaki");
        customer.setCustIndustry("峡谷之巅");
        dao.save(customer);
    }

    @Test
    public void testUpdate() {
        Customer customer  = new Customer();
        customer.setCustId(5l);
        customer.setCustName("hasaki");
        customer.setCustIndustry("废铜烂铁");
        dao.save(customer);
    }

    /**
     * 测试删除
     */
    @Test
    public void testDelete(){
        dao.delete(2l);
    }

    /**
     * 查询所有
     */
    @Test
    public void testFindAll() {
        List<Customer> list = dao.findAll();
        for(Customer customer : list) {
            System.out.println(customer);
        }
    }

    /**
     * 统计查询
     */
    /**
     * 测试统计查询：查询客户的总数量
     *      count:统计总条数
     */
    @Test
    public void testCount() {
        long count = dao.count();//查询全部的客户数量
        System.out.println(count);
    }

    /**
     * 测试：判断id为4的客户是否存在
     *      1. 可以查询以下id为4的客户
     *          如果值为空，返回false，如果不为空，返回true
     */
    @Test
    public void  testExists() {
        boolean exists = dao.exists(4l);
        System.out.println("id为4的客户 是否存在："+exists);
    }

}

6.JPQL(配置在接口方法上，使用@Query)

package org.maple.dao;

import org.maple.domain.Customer;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;

/**
 * @author mapleins
 * @Date 2019-01-10 21:40
 * @Desc 使用Jpql
 **/
public interface CustomerDao2 extends JpaRepository<Customer,Long>, JpaSpecificationExecutor<Customer> {

    /**
     * 根据名字查询
     */
    @Query("from Customer where custName = ?")
    Customer findJpql(String custName);

    /**
     * 根据客户名称和客户id查询客户
     * 参数位置需要一致
     *   或者
     *     @Query("from Customer where custName = ?2 and custId = ?1")
     *     Customer findJpql2(Long id,String custName);
     */
    @Query("from Customer where custName = ? and custId = ?")
    Customer findJpql2(String custName,Long id);

    /**
     * 使用jpql完成更新操作
     *      案例 ： 根据id更新，客户的名称
     *          更新4号客户的名称，将名称改为“黑马程序员”
     *
     *  sql  ：update cst_customer set cust_name = ? where cust_id = ?
     *  jpql : update Customer set custName = ? where custId = ?
     *
     *  @Query : 代表的是进行查询
     *      * 声明此方法是用来进行更新操作
     *  @Modifying
     *      * 当前执行的是一个更新操作
     *
     */
    @Query("update Customer set custName = ?2 where custId = ?1")
    @Modifying
    void updateCustomer(Long custId,String custName);
}

package org.maple.test;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.maple.dao.CustomerDao2;
import org.maple.domain.Customer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.annotation.Rollback;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;

/**
 * @author mapleins
 * @Date 2019-01-10 21:42
 * @Desc
 **/
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class CustomerDao2Test {

    @Autowired
    private CustomerDao2 dao;

    @Test
    public void findJpql(){
        Customer hasaki = dao.findJpql("hasaki");
        System.out.println(hasaki);
    }

    @Test
    public void findJpq2(){
        Customer hasaki = dao.findJpql2("hasaki",5l);
        System.out.println(hasaki);
    }

    /**
     * 测试jpql的更新操作
     *  * springDataJpa中使用jpql完成 更新/删除操作
     *         * 需要手动添加事务的支持
     *         * 默认会执行结束之后，回滚事务
     *   @Rollback : 设置是否自动回滚
     *          false | true
     */
    @Test
    @Transactional //添加事务的支持
    @Rollback(value = false)
    public void testUpdateCustomer() {
        dao.updateCustomer(4l,"coward");
    }
}

7.SQL语句查询

package org.maple.dao;

import org.maple.domain.Customer;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;

import java.util.List;

/**
 * @author mapleins
 * @Date 2019-01-10 21:54
 * @Desc 使用Sql
 **/
public interface CustomerDao3 extends JpaRepository<Customer,Long>, JpaSpecificationExecutor<Customer> {

    @Query(value = "select * from cst_customer",nativeQuery = true)
    List<Object[]> findSql();

    @Query(value = "select * from cst_customer where cust_name like ?1",nativeQuery = true)
    List<Object[]> findSql2(String name);
}

package org.maple.test;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.maple.dao.CustomerDao2;
import org.maple.dao.CustomerDao3;
import org.maple.domain.Customer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.annotation.Rollback;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;

import java.util.Arrays;
import java.util.List;

/**
 * @author mapleins
 * @Date 2019-01-10 21:42
 * @Desc
 **/
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class CustomerDao3Test {

    @Autowired
    private CustomerDao3 dao;

    @Test
    public void findSql(){
        List<Object[]> list = dao.findSql();
        for (Object[] obj : list) {
            System.out.println(Arrays.toString(obj));
        }
    }

    @Test
    public void findSql2(){
        List<Object[]> list = dao.findSql2("%a%");
        for (Object[] obj : list) {
            System.out.println(Arrays.toString(obj));
        }
    }

}

8.方法名称规则

*我们只需要按照SpringDataJpa提供的方法名称规则定义方法，不需要再配置jpql语句，完成查询
　　findBy开头： 代表查询
　　对象中属性名称（首字母大写）
　　*含义：根据属性名称进行查询

package org.maple.dao;

import org.maple.domain.Customer;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

import java.util.List;

/**
 * @author mapleins
 * @Date 2019-01-10 22:03
 * @Desc
 **/
public interface CustomerDao4 extends JpaRepository<Customer,Long>, JpaSpecificationExecutor<Customer> {

    List<Customer> findCustomerByCustNameLike(String name);

    Customer findCustomerByCustNameAndCustIndustry(String name,String industry);
}

package org.maple.test;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.maple.dao.CustomerDao;
import org.maple.dao.CustomerDao4;
import org.maple.domain.Customer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

/**
 * @author mapleins
 * @Date 2019-01-10 21:22
 * @Desc
 **/
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class CustomerDao4Test {

    @Autowired
    private CustomerDao4 dao;

    @Test
    public void findLike(){
        List<Customer> customers = dao.findCustomerByCustNameLike("%a%");
        for (Customer customer : customers) {
            System.out.println(customer);
        }
    }

    @Test
    public void findNameAndIndustry(){
        Customer customer = dao.findCustomerByCustNameAndCustIndustry("hasaki","废铜烂铁");
        System.out.println(customer);
    }

}

 9.Spec Sort PageRequest

package org.maple.test;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.maple.dao.CustomerDao;
import org.maple.domain.Customer;
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.data.jpa.domain.Specification;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;

import javax.persistence.criteria.*;
import java.util.List;

/**
 * @author mapleins
 * @Date 2019-01-10 21:22
 * @Desc
 **/
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class CustomerDaoTest {

    @Autowired
    private CustomerDao dao;

    /**
     * 查询单个参数
     */
    @Test
    public void testSpec(){
        Specification<Customer> spec = new Specification<Customer>() {
            /**
             * 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hasaki的客户
             *          查询条件
             *              1.查询方式
             *                  cb对象
             *              2.比较的属性名称
             *                  root对象
             *
             */
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                //1.获取比较的属性
                Path<Object> custName = root.get("custName");
                //2.构造查询条件
                /**
                 * 1.需要比较的属性 path对象
                 * 2.需要比较的取值
                 */
                Predicate predicate = cb.equal(custName, "hasaki");
                return predicate;
            }
        };
        Customer customer = dao.findOne(spec);
        System.out.println(customer);
    }

    /**
     * 多条件查询
     * 根据名字hasaki 和行业查询 废铜烂铁
     */
    @Test
    public void testSpec2(){
        Specification<Customer> spec = new Specification<Customer>() {
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                Path<Object> custName = root.get("custName");
                Path<Object> custIndustry = root.get("custIndustry");
                Predicate p1 = cb.equal(custName, "hasaki");
                Predicate p2 = cb.equal(custIndustry, "废铜烂铁");
                //and 与
                //or 或
                Predicate predicate = cb.and(p1, p2);
                return predicate;
            }
        };
        Customer customer = dao.findOne(spec);
        System.out.println(customer);
    }

    /**
     * 模糊查询返回列表
     * 查询名字包含r的
     * gt lt je le like :得到path ,根据path 指定比较的参数类型，再比较
     */
    @Test
    public void testSpec3(){
        Specification<Customer> spec = new Specification<Customer>() {
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                Path<Object> custName = root.get("custName");
                //path对象指定的参数类型
                Predicate predicate = cb.like(custName.as(String.class), "%r%");
                return predicate;
            }
        };
        List<Customer> list = dao.findAll(spec);
        System.out.println(list);
    }

    /**
     * 排序
     */
    @Test
    public void testSpec4(){
        Specification<Customer> spec = new Specification<Customer>() {
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                Path<Object> custName = root.get("custName");
                //path对象指定的参数类型
                Predicate predicate = cb.like(custName.as(String.class), "%r%");
                return predicate;
            }
        };
        //1.升序或降序 2.属性名
        Sort sort = new Sort(Sort.Direction.DESC,"custId");
        List<Customer> list = dao.findAll(spec,sort);
        System.out.println(list);
    }

    /**
     * 分页
     */
    @Test
    public void testSpec5(){
        Specification<Customer> spec = null ;
        //分页 从0开始，每页2条
        PageRequest pageRequest = new PageRequest(0, 1);
        Page<Customer> page = dao.findAll(spec, pageRequest);
        System.out.println(page.getContent());//数据集合列表
        System.out.println(page.getTotalElements());//总条数
        System.out.println(page.getTotalPages());//总页数


    }


}