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.RELEASEspring.version>
<hibernate.version>5.0.7.Finalhibernate.version>
<slf4j.version>1.6.6slf4j.version>
<log4j.version>1.2.12log4j.version>
<c3p0.version>0.9.1.2c3p0.version>
<mysql.version>5.1.6mysql.version>
properties>
<dependencies>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.9version>
<scope>testscope>
dependency>
<dependency>
<groupId>org.aspectjgroupId>
<artifactId>aspectjweaverartifactId>
<version>1.6.8version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-aopartifactId>
<version>${spring.version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-contextartifactId>
<version>${spring.version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-context-supportartifactId>
<version>${spring.version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-ormartifactId>
<version>${spring.version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-beansartifactId>
<version>${spring.version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-coreartifactId>
<version>${spring.version}version>
dependency>
<dependency>
<groupId>org.hibernategroupId>
<artifactId>hibernate-coreartifactId>
<version>${hibernate.version}version>
dependency>
<dependency>
<groupId>org.hibernategroupId>
<artifactId>hibernate-entitymanagerartifactId>
<version>${hibernate.version}version>
dependency>
<dependency>
<groupId>org.hibernategroupId>
<artifactId>hibernate-validatorartifactId>
<version>5.2.1.Finalversion>
dependency>
<dependency>
<groupId>c3p0groupId>
<artifactId>c3p0artifactId>
<version>${c3p0.version}version>
dependency>
<dependency>
<groupId>log4jgroupId>
<artifactId>log4jartifactId>
<version>${log4j.version}version>
dependency>
<dependency>
<groupId>org.slf4jgroupId>
<artifactId>slf4j-apiartifactId>
<version>${slf4j.version}version>
dependency>
<dependency>
<groupId>org.slf4jgroupId>
<artifactId>slf4j-log4j12artifactId>
<version>${slf4j.version}version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>${mysql.version}version>
dependency>
<dependency>
<groupId>org.springframework.datagroupId>
<artifactId>spring-data-jpaartifactId>
<version>1.9.0.RELEASEversion>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-testartifactId>
<version>4.2.4.RELEASEversion>
dependency>
<dependency>
<groupId>javax.elgroupId>
<artifactId>javax.el-apiartifactId>
<version>2.2.4version>
dependency>
<dependency>
<groupId>org.glassfish.webgroupId>
<artifactId>javax.elartifactId>
<version>2.2.4version>
dependency>
dependencies>
<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">
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="packagesToScan" value="com.zy.domain"/>
<property name="persistenceProvider">
<bean class="org.hibernate.jpa.HibernatePersistenceProvider"/>
property>
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="generateDdl" value="false"/>
<property name="database" value="MYSQL"/>
<property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect"/>
<property name="showSql" value="true"/>
bean>
property>
<property name="jpaDialect">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect"/>
property>
bean>
<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&characterEncoding=UTF-8" />
<property name="user" value="root" />
<property name="password" value="1111" />
bean>
<jpa:repositories base-package="com.zy.dao" transaction-manager-ref="transactionManager"
entity-manager-factory-ref="entityManagerFactory">
jpa:repositories>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory"/>
bean>
<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
}
}