背景
考慮到公司應用中數據庫訪問的多樣性和複雜性,目前正在開發UDSL(統一數據訪問層),開發到一半的時候,偶遇SpringData 工程。發現兩者的思路驚人的一致。
於是就花了點時間瞭解SpringData,可能UDSL II期會基於SpringData做擴展
SpringData相關資料
介紹:針對關係型數據庫,KV數據庫,Document數據庫,Graph數據庫,Map-Reduce等一些主流數據庫,採用統一技術進行訪問,並且儘可能簡化訪問手段。
目前已支持的數據庫有(主要):MongoDB,Neo4j,Redis,Hadoop,JPA等
SpringData官方資料(強烈推薦,文檔非常詳細)
SpringData主頁:http://www.springsource.org/spring-data
SpringDataJPA 指南文檔:http://static.springsource.org/spring-data/data-jpa/docs/current/reference/html/ (非常詳細)
SpringDataJPA Examples: https://github.com/SpringSource/spring-data-jpa-examples (非常詳細的例子)
Spring-Data-Jpa簡介
Spring Data Jpa 極大簡化了數據庫訪問層代碼,只要3步,就能搞定一切
1. 編寫Entity類,依照JPA規範,定義實體
2. 編寫Repository接口,依靠SpringData規範,定義數據訪問接口(注意,只要接口,不需要任何實現)
3. 寫一小陀配置文件 (Spring Scheme配置方式極大地簡化了配置方式)
下面,我依賴Example中的例子,簡單地介紹下以上幾個步驟
User.java
1 /**
2 * User Entity Sample
3 *
4 * @author <a href="mailto:[email protected]">Stone.J</a> Aug 25, 2011
5 */
6 @Entity
7 public class User extends AbstractPersistable < Long > {
8
9 private static final long serialVersionUID = - 2952735933715107252L ;
10
11 @Column(unique = true )
12 private String username;
13 private String firstname;
14 private String lastname;
15
16 public String getUsername() {
17 return username;
18 }
19
20 public void setUsername(String username) {
21 this .username = username;
22 }
23
24 public String getFirstname() {
25 return firstname;
26 }
27
28 public void setFirstname(String firstname) {
29 this .firstname = firstname;
30 }
31
32 public String getLastname() {
33 return lastname;
34 }
35
36 public void setLastname(String lastname) {
37 this .lastname = lastname;
38 }
39
沒什麼技術,JPA規範要求怎麼寫,它就怎麼寫
Repository.java
1 /**
2 * User Repository Interface.
3 *
4 * @author <a href="mailto:[email protected]">Stone.J</a> Aug 25, 2011
5 */
6 public interface SimpleUserRepository extends CrudRepository < User, Long > , JpaSpecificationExecutor <User > {
7
8 public User findByTheUsersName(String username);
9
10 public List < User > findByLastname(String lastname);
11
12 @Query( " select u from User u where u.firstname = ? " )
13 public List < User > findByFirstname(String firstname);
14
15 @Query( " select u from User u where u.firstname = :name or u.lastname = :name " )
16 public List < User > findByFirstnameOrLastname(@Param( " name " ) String name);
17
18
需要關注它繼承的接口,我簡單介紹幾個核心接口
不需要寫任何實現類,Spring Data Jpa框架幫你搞定這一切。
Spring Configuration
1 < beans >
2 < bean id = " entityManagerFactory " class = "org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean " >
3 < property name = " dataSource " ref = " dataSource " />
4 < property name = " jpaVendorAdapter " >
5 < bean class = " org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter " >
6 < property name = " generateDdl " value = " true " />
7 < property name = " database " value = " HSQL " />
8 </ bean >
9 </ property >
10 < property name = " persistenceUnitName " value = " jpa.sample " />
11 </ bean >
12
13 < bean id = " transactionManager " class = " org.springframework.orm.jpa.JpaTransactionManager " >
14 < property name = " entityManagerFactory " ref = " entityManagerFactory " />
15 </ bean >
16
17 < jdbc:embedded - database id = " dataSource " type = " HSQL " />
18
19
20 < jpa:repositories base - package = " org.springframework.data.jpa.example.repository.simple " />
21 </ beans>
核心代碼只要配置一行:<jpa:repositories base-package="org.springframework.data.jpa.example.repository.simple" />即可。上面的僅僅是數據源,事務的配置而已。
至此,大功告成,即可運行
1 /**
2 * Intergration test showing the basic usage of { @link SimpleUserRepository}.
3 *
4 * @author <a href="mailto:[email protected]">Stone.J</a> Aug 25, 2011
5 */
6 @RunWith(SpringJUnit4ClassRunner. class )
7 @ContextConfiguration(locations = " classpath:simple-repository-context.xml " )
8 @Transactional
9 public class SimpleUserRepositorySample {
10
11 @Autowired
12 SimpleUserRepository repository;
13 User user;
14
15 @Before
16 public void setUp() {
17 user = new User();
18 user.setUsername( " foobar " );
19 user.setFirstname( " firstname " );
20 user.setLastname( " lastname " );
21 }
22
23 // crud方法測試
24 @Test
25 public void testCrud() {
26 user = repository.save(user);
27 assertEquals(user, repository.findOne(user.getId()));
28 }
29
30 // method query測試
31 @Test
32 public void testMethodQuery() throws Exception {
33 user = repository.save(user);
34 List < User > users = repository.findByLastname( " lastname " );
35 assertNotNull(users);
36 assertTrue(users.contains(user));
37 }
38
39 // named query測試
40 @Test
41 public void testNamedQuery() throws Exception {
42 user = repository.save(user);
43 List < User > users = repository.findByFirstnameOrLastname( " lastname " );
44 assertTrue(users.contains(user));
45 }
46
47 // criteria query測試
48 @Test
49 public void testCriteriaQuery() throws Exception {
50 user = repository.save(user);
51 List < User > users = repository.findAll( new Specification < User > () {
52
53 @Override
54 public Predicate toPredicate(Root < User > root, CriteriaQuery <?> query, CriteriaBuilder cb) {
55 return cb.equal(root.get( " lastname " ), " lastname " );
56 }
57 });
58 assertTrue(users.contains(user));
59 }
60
其中,寫操作相對比較簡單,我不做詳細介紹,針對讀操作,我稍微描述下:
Method Query: 方法級別的查詢,針對
findBy
, find
, readBy
, read
, getBy等前綴的方法,解析方法字符串,生成查詢語句,其中支持的關鍵詞有:
Named Query: 針對一些複雜的SQL,支持原生SQL方式,進行查詢,保證性能
Criteria Query: 支持JPA標準中的Criteria Query