SpringData JPA快速入门和基本的CRUD操作以及Specifications条件查询
SpringData JPA概述：
SpringData JPA 是 Spring 基于 ORM 框架、JPA 规范的基础上封装的一套JPA应用框架，可使开发者用极简的代码即可实现对数据库的访问和操作。
它提供了包括增删改查等在内的常用功能，且易于扩展！学习并使用 SpringData JPA 可以极大提高开发效率！
SpringData JPA 让我们解脱了DAO层的操作，基本上所有CRUD都可以依赖于它来实现,在实际的工作工程中，
推荐使用SpringData JPA + ORM（如：hibernate）完成操作，这样在切换不同的ORM框架时提供了极大的方便，同时也使数据库层操作更加简单，方便解耦
SpringData JPA的快速入门：
1.引入SpringData JPA和操作数据库相关的坐标
<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 AOP --> <dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjweaver</artifactId> <version>1.6.8</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aop</artifactId> <version>${spring.version}</version> </dependency> <!-- spring IOC --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context-support</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> </dependency> <!-- spring对orm框架的支持 --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-orm</artifactId> <version>${spring.version}</version> </dependency> <!-- hibernate --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>${hibernate.version}</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator</artifactId> <version>5.2.1.Final</version> </dependency> <!-- hibernate对JPA的实现 --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>${hibernate.version}</version> </dependency> <!-- c3p0 --> <dependency> <groupId>c3p0</groupId> <artifactId>c3p0</artifactId> <version>${c3p0.version}</version> </dependency> <!-- log --> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>${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> <!-- 数据库驱动 --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>${mysql.version}</version> </dependency> <!-- spring data jpa --> <dependency> <groupId>org.springframework.data</groupId> <artifactId>spring-data-jpa</artifactId> <version>1.9.0.RELEASE</version> </dependency> <!-- spring 测试 --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>${spring.version}</version> </dependency> <!-- el 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> </dependencies>
2.整合Spring Data JPA与Spring
<?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" 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"> <!-- 开启注解扫描 --> <context:component-scan base-package="com.fgy"></context:component-scan> <!-- 创建entityManagerFactory对象交给spring容器管理--> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <!-- 配置数据源 --> <property name="dataSource" ref="dataSource"></property> <!-- 配置扫描实体类所在的包 --> <property name="packagesToScan" value="com.fgy.domain"></property> <!-- 配置JPA的实现厂家 --> <property name="persistenceProvider"> <bean class="org.hibernate.jpa.HibernatePersistenceProvider"></bean> </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="true" /> <!--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"></bean> </property> <!-- 注入jpa的配置信息 加载jpa的基本配置信息和jpa实现方式（这里是hibernate）的配置信息 --> <property name="jpaProperties"> <props> <!-- 自动创建数据库表 create update none --> <prop key="hibernate.hbm2ddl.auto">update</prop> <!-- 格式化SQL语句 --> <prop key="hibernate.format_sql">true</prop> </props> </property> </bean> <!-- 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> <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/jpa"></property> <property name="user" value="root"></property> <property name="password" value="root"></property> </bean> <!-- 整合spring data jpa --> <jpa:repositories base-package="com.fgy.dao" transaction-manager-ref="transactionManager" entity-manager-factory-ref="entityManagerFactory"></jpa:repositories> <!-- 配置事务管理器 --> <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory"/> </bean> <!-- 配置事务的通知 --> <tx:advice id="txAdvice" transaction-manager="transactionManager"> <!-- 配置事务属性 --> <tx:attributes> <tx:method name="*" read-only="false" propagation="REQUIRED"/> <tx:method name="find*" read-only="true" propagation="SUPPORTS"/> </tx:attributes> </tx:advice> <!-- 配置aop --> <aop:config> <!-- 配置切入点表达式 --> <aop:pointcut id="pt" expression="execution(* com.fgy.service.impl.*.*(..))"/> <aop:advisor advice-ref="txAdvice" pointcut-ref="pt"/> </aop:config> </beans>
3.使用JPA注解配置实体类和表的映射关系
@Entity @Table(name = "cst_customer") public class Customer implements Serializable { @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; /*************** get和set方法 ***************/
4.编写符合Spring Data JPA规范的Dao层接口
Spring Data JPA是spring提供的一款对于数据访问层（Dao层）的框架，
使用Spring Data JPA，只需要按照框架的规范提供dao接口，不需要实现类就可以完成数据库的增删改查、分页查询等方法的定义，极大的简化了我们的开发过程
在Spring Data JPA中，对于定义符合规范的Dao层接口，需要遵循以下几点：
1.创建一个Dao层接口，并实现JpaRepository和JpaSpecificationExecutor
2.提供相应的泛型
/** * 客户持久层接口 * * JpaRepository<实体类类型，主键类型>：用来完成基本CRUD操作 * JpaSpecificationExecutor<实体类类型>：用于复杂查询（分页等查询操作） */ public interface CustomerDao extends JpaRepository<Customer, Long>, JpaSpecificationExecutor<Customer> { }
5.测试
@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = "classpath:applicationContext.xml") public class CustomerDaoTest { @Autowired private CustomerDao customerDao; @Test public void testFindAll() { List<Customer> customers = customerDao.findAll(); for (Customer customer : customers) { System.out.println(customer); } } }
测试其他方法：
/** * 修改客户：调用save(obj)方法 * 如果执行此方法,参数对象中存在id属性，即为更新操作,会先根据id查询，再更新 * 如果执行此方法中对象中不存在id属性，即为保存操作 */ @Test public void testSave() { // 根据id查询id为1的客户 Customer c1 = customerDao.findOne(5L); // 修改客户名称 c1.setCustName("不三不四"); // 更新数据 // customerDao.save(c1); Customer c2 = new Customer(); c2.setCustName("小倩"); // 插入数据 customerDao.save(c2); }
/** * 根据id查询一条记录 */ @Test public void testFindById() { Customer customer = customerDao.findOne(5L); System.out.println(customer); }
/** * 删除一条记录 */ @Test public void testDelete() { customerDao.delete(5L); }
在 JpaRepository 接口以及父接口（灰色为父接口继承过来的方法）中已经声明了多个操作数据库的方法，可以直接使用
JpaSpecificationExecutor接口的方法
Specification接口中只定义了如下一个方法：
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);
cb中方法的对应关系：
使用Specifications完成条件查询：
1.持久层接口
/** * 客户持久层接口 * * JpaRepository<实体类类型，主键类型>：用来完成基本CRUD操作 * JpaSpecificationExecutor<实体类类型>：用于复杂查询（分页等查询操作） */ public interface CustomerDao extends JpaRepository<Customer, Long>, JpaSpecificationExecutor<Customer> { }
2.测试
@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 * 根据客户名称查询 */ @Test public void testSpec() { Specification<Customer> spec = new Specification<Customer>() { @Override public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) { Path<Object> custName = root.get("custName"); // 构造查询条件 Predicate predicate = cb.equal(custName, "小明");// 进行精准的匹配 return predicate; } }; Customer c = customerDao.findOne(spec); System.out.println(c); } /** * 多条件查询 * 根据客户名和客户行业查询 */ @Test public void testSpec2() { Customer c = customerDao.findOne(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, "小倩"); Predicate p2 = cb.equal(custIndustry, "教育"); // 将多个查询条件组合到一起 // 与的形式 return cb.and(p1, p2); // 或的形式 // return cb.or(p1, p2); } }); System.out.println(c); } /** * 根据客户名模糊匹配 * 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() { List<Customer> customers = customerDao.findAll(new Specification<Customer>() { @Override public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) { Path<Object> custName = root.get("custName"); return cb.like(custName.as(String.class), "小%"); } }); for (Customer customer : customers) { System.out.println(customer); } } /** * 根据条件查询，然后排序 */ @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"); return cb.like(custName.as(String.class), "小%"); } }; // 参数1：排序顺序（正序，倒序） // 参数2：排序属性名称 Sort sort = new Sort(Sort.Direction.DESC, "custId"); List<Customer> customers = customerDao.findAll(spec, sort); for (Customer customer : customers) { System.out.println(customer); } } /** * 分页查询 * findAll(Specification, Pageable) * 参数1：查询条件 * 参数2：分页参数(查询页码，每页查询条数) * findAll(Pageable) 没有条件的分页 */ @Test public void testSpec5() { Specification spec = null; Pageable pageable = new PageRequest(0, 2); Page<Customer> page = customerDao.findAll(spec, pageable); List<Customer> customers = page.getContent(); // 得到数据集合列表 long totalCount = page.getTotalElements(); // 得到总记录数 int totalPages = page.getTotalPages();// 得到总页数 for (Customer customer : customers) { System.out.println(customer); } System.out.println(totalCount); System.out.println(totalPages); } /** * 根据条件统计记录 */ @Test public void testSpec6() { long count = customerDao.count(new Specification<Customer>() { @Override public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) { Path<Object> industry = root.get("custIndustry"); return cb.isNull(industry); } }); System.out.println(count); } }
