Spring Data JPA——Specifications动态查询

一、Specifications动态查询

有时我们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。

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

参数:
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

1、pom文件和applicationContext.xml文件

    <properties>
        <spring.version>4.2.4.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>4.9</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>

        <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>

        <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>4.2.4.RELEASE</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 -->
    </dependencies>

<?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="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!-- 配置要扫描的实体类包 -->
        <property name="packagesToScan" value="com.zy.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 -->
                <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="driverClass" value="com.mysql.jdbc.Driver" />
        <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/jpa?useUnicode=true&amp;characterEncoding=UTF-8" />
        <property name="user" value="root" />
        <property name="password" value="1111" />
    </bean>

    <!-- 3. 整合spring data Jpa -->
    <jpa:repositories base-package="com.zy.dao" transaction-manager-ref="transactionManager"
        entity-manager-factory-ref="entityManagerFactory">
    </jpa:repositories>

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

    <!-- 5. 配置声明式事务(这里先不配置) -->

    <!-- 6. 配置包扫描 -->
    <context:component-scan base-package="com.zy"/>


</beans>

dao

public interface CustomerDao extends JpaRepository<Customer, Long>, JpaSpecificationExecutor<Customer> {
}

domain

/**
 * 1.实体类和表的映射关系
 *      @Eitity
 *      @Table
 * 2.类中属性和表中字段的映射关系
 *      @Id
 *      @GeneratedValue
 *      @Column
 */
@Entity
@Table(name = "cst_customer")
public class Customer {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="cust_id")
    private Long custId;
    
    @Column(name="cust_address")
    private String custAddress;
    
    @Column(name="cust_industry")
    private String custIndustry;
    
    @Column(name="cust_level")
    private String custLevel;
    
    @Column(name="cust_name")
    private String custName;
    
    @Column(name="cust_phone")
    private String custPhone;
    
    @Column(name="cust_source")
    private String custSource;
}

2、单条件、多条件、模糊、排序、分页等查询实现

/**
 * Description:
 *
 * @author zygui
 * @date 2020/5/6 08:40
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class SpecTest {

    @Autowired
    private CustomerDao customerDao;

    /**
     * 根据条件, 查询单个对象
     */
    @Test
    public void testSpec () {
        // 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
         *                  cb对象
         *              2.比较的属性名称
         *                  root对象
         *
         */
        Specification<Customer> spec = new Specification<Customer>() {
            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 = '桂朝阳'
                /**
                 * 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, "桂朝阳");
                return predicate;
            }
        };
        Customer customer = customerDao.findOne(spec);
        System.out.println("customer = " + customer);
    }

    /**
     * 多条件查询
     *      案例：根据客户名（cust_name）和客户所属行业查询（xxx）
     *
     */
    @Test
    public void testSpec1() {
        /**
         *  root:获取属性
         *      客户名
         *      所属行业
         *  cb：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>() {
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                Path<Object> custName = root.get("custName"); // 客户名
                Path<Object> custIndustry = root.get("custIndustry"); // 所属行业

                // 构造查询
                //1. 构造客户名的精准匹配查询
                Predicate p1 = criteriaBuilder.equal(custName, "老虎");
                //2..构造所属行业的精准匹配查询
                Predicate p2 = criteriaBuilder.equal(custIndustry, "animal");
                //3. 将多个查询条件组合起来: 组合; And Or
                Predicate p3 = criteriaBuilder.and(p1, p2); // 以`与`的形式拼接多个查询条件
                return p3;
            }
        };
        Customer customer = customerDao.findOne(spec);
        System.out.println("customer = " + customer);
    }


    /**
     * 案例：完成根据客户名称的模糊匹配，返回客户列表
     *      客户名称以 ’桂‘ 开头
     *
     * 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 testSpec3() {
        // 构造查询条件
        Specification<Customer> spec = new Specification<Customer>() {
            public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //查询属性：客户名
                Path<Object> custName = root.get("custName");
                //查询方式：模糊匹配
                Predicate predicate = criteriaBuilder.like(custName.as(String.class), "桂%");
                return predicate;
            }
        };
        List<Customer> list = customerDao.findAll(spec);
        for (Customer customer : list) {
            System.out.println("customer = " + customer);
        }
    }

    @Test
    public void testSpec10() {
        // 构造查询条件
        Specification<Customer> spec = new Specification<Customer>() {
            public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //查询属性：客户名
                Path<Object> custName = root.get("custName");
                //查询方式：模糊匹配
                Predicate predicate = criteriaBuilder.like(custName.as(String.class), "桂%");
                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.Direction.DESC:倒序
        //   Sort.Direction.ASC ： 升序
        //第二个参数：排序的属性名称
        Sort sort = new Sort(Sort.Direction.DESC, "custId");
        List<Customer> list = customerDao.findAll(spec, sort);
        for (Customer customer : list) {
            System.out.println("customer = " + customer);
        }
    }

    /**
     * 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 testSpec4() {
        Specification<Customer> spec = null;
        //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 = new PageRequest(0, 2);
        // 分页查询
        Page<Customer> page = customerDao.findAll(null, 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
    }
}