SpringDataJPA是Spring Data的一个子项目，通过提供基于JPA的Repository极大的减少了JPA作为数据访问方案的代码量，你仅仅需要编写一个接口集成下SpringDataJPA内部定义的接口即可完成简单的CRUD操作。

前言

本篇文章引导你通过Spring Boot，Spring Data JPA和MySQL实现设置@id @generatedvalue初始值从10000自增。

准备

• JDK 1.8 或更高版本
• Maven 3 或更高版本
• MySQL Server 5.6

技术栈

• Spring Data JPA
• Spring Boot
• MySQL

目录结构

父pom.xml

<?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">     <modelVersion>4.0.0</modelVersion>      <groupId>cn.merryyou</groupId>     <artifactId>jpa-example</artifactId>     <version>1.0-SNAPSHOT</version>     <modules>         <module>one-to-one-foreignkey</module>         <module>one-to-one-primarykey</module>         <module>one-to-many</module>         <module>many-to-many</module>         <module>many-to-many-extra-columns</module>         <module>initial-value-generator</module>     </modules>     <packaging>pom</packaging>       <dependencyManagement>         <dependencies>             <dependency>                 <groupId>io.spring.platform</groupId>                 <artifactId>platform-bom</artifactId>                 <version>Brussels-SR6</version>                 <type>pom</type>                 <scope>import</scope>             </dependency>         </dependencies>     </dependencyManagement> </project> 

@id @generatedvalue设置初始值

目录结构

pom.xml

<?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>jpa-example</artifactId>         <groupId>cn.merryyou</groupId>         <version>1.0-SNAPSHOT</version>     </parent>     <modelVersion>4.0.0</modelVersion>      <artifactId>initial-value-generator</artifactId>      <properties>         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>         <java.version>1.8</java.version>     </properties>      <dependencies>         <dependency>             <groupId>org.springframework.boot</groupId>             <artifactId>spring-boot-starter-data-jpa</artifactId>         </dependency>          <dependency>             <groupId>mysql</groupId>             <artifactId>mysql-connector-java</artifactId>             <scope>runtime</scope>         </dependency>          <dependency>             <groupId>org.projectlombok</groupId>             <artifactId>lombok</artifactId>         </dependency>          <dependency>             <groupId>org.springframework.boot</groupId>             <artifactId>spring-boot-starter-test</artifactId>             <scope>test</scope>         </dependency>     </dependencies>      <build>         <plugins>             <plugin>                 <groupId>org.springframework.boot</groupId>                 <artifactId>spring-boot-maven-plugin</artifactId>             </plugin>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-compiler-plugin</artifactId>                 <version>3.6.1</version>                 <configuration>                     <source>1.8</source>                     <target>1.8</target>                 </configuration>             </plugin>         </plugins>     </build>  </project> 

db.sql

SET FOREIGN_KEY_CHECKS=0;  -- ---------------------------- -- Table structure for address -- ---------------------------- DROP TABLE IF EXISTS `address`; CREATE TABLE `address` (   `id` bigint(20) NOT NULL,   `city` varchar(255) DEFAULT NULL,   `state` varchar(255) DEFAULT NULL,   `street` varchar(255) DEFAULT NULL,   `zip` varchar(255) DEFAULT NULL,   PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;  -- ---------------------------- -- Records of address -- ----------------------------  -- ---------------------------- -- Table structure for app_seq_store -- ---------------------------- DROP TABLE IF EXISTS `app_seq_store`; CREATE TABLE `app_seq_store` (   `APP_SEQ_NAME` varchar(255) NOT NULL,   `APP_SEQ_VALUE` int(11) NOT NULL,   PRIMARY KEY (`APP_SEQ_NAME`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;  -- ---------------------------- -- Records of app_seq_store -- ---------------------------- INSERT INTO `app_seq_store` VALUES ('LISTENER_PK', '10000');  

实体类

Address

@Entity public class Address {     @Id     @Column( name = "ID" )     @TableGenerator(             name = "AppSeqStore",             table = "APP_SEQ_STORE",             pkColumnName = "APP_SEQ_NAME",             pkColumnValue = "LISTENER_PK",             valueColumnName = "APP_SEQ_VALUE",             initialValue = 10000,             allocationSize = 1 )     @GeneratedValue( strategy = GenerationType.TABLE, generator = "AppSeqStore" )     private long id;      private String street;      private String city;      private String state;      private String zip;      public long getId() {         return id;     }      public void setId(long id) {         this.id = id;     }      public String getStreet() {         return street;     }      public void setStreet(String address) {         this.street = address;     }      public String getCity() {         return city;     }      public void setCity(String city) {         this.city = city;     }      public String getState() {         return state;     }      public void setState(String state) {         this.state = state;     }      public String getZip() {         return zip;     }      public void setZip(String zip) {         this.zip = zip;     }      public String toString() {         return "Address id: " + getId() + ", street: " + getStreet() + ", city: " + getCity()                 + ", state: " + getState() + ", zip: " + getZip();     } 

• @Table声明此对象映射到数据库的数据表，通过它可以为实体指定表(talbe),目录(Catalog)和schema的名字。该注释不是必须的，如果没有则系统使用默认值(实体的短类名)。

• @Id 声明此属性为主键。该属性值可以通过应该自身创建，但是Hibernate推荐通过Hibernate生成

• @GeneratedValue 指定主键的生成策略。

  1. TABLE：使用表保存id值
  2. IDENTITY：identitycolumn
  3. SEQUENCR ：sequence
  4. AUTO：根据数据库的不同使用上面三个

• @Column 声明该属性与数据库字段的映射关系。

• name 声明该表主键生成策略的名称，它被引用在@GeneratedValue中设置的“generator”值中;

• table 声明表生成策略所持久化的表名;

• pkColumnName 声明在持久化表中，该主键生成策略所对应键值的名称;

• valueColumnName 声明在持久化表中，该主键当前所生成的值，它的值将会随着每次创建累加;

• pkColumnValue 声明在持久化表中，该生成策略所对应的主键。

• initialValue 声明主键初识值，默认为0

• allocationSize 声明每次主键值增加的大小

Spring Data JPA Repository

AddressRepository

public interface AddressRepository extends JpaRepository<Address, Integer> { } 

Spring Data JPA包含了一些内置的Repository，实现了一些常用的方法：findone，findall，save等。

application.yml

spring:   datasource:     url: jdbc:mysql://localhost/initial-value-generator     username: root     password: admin     driver-class-name: com.mysql.jdbc.Driver   jpa:     show-sql: true     properties:       hibernate:         enable_lazy_load_no_trans: true #    hibernate: #      ddl-auto: create 

AddressRepositoryTest

@RunWith(SpringRunner.class) @SpringBootTest @Slf4j public class AddressRepositoryTest {      @Autowired     private AddressRepository addressRepository;      @Test     public void testSave(){         Address address = new Address();         address.setCity("beijing");         address.setState("02");         address.setStreet("street");         address.setZip("aa.zip");         Address result = addressRepository.save(address);         Assert.assertNotNull(result);         Assert.assertNotNull(result.getId());         Assert.assertTrue(result.getId()>=10000);     } } 

代码下载

从我的 github 中下载，https://github.com/longfeizheng/jpa-example/tree/master/initial-value-generator

1. JPA关系映射系列一：one-to-one外键关联
2. JPA关系映射系列二：one-to-one主键关联
3. JPA关系映射系列三：one-to-many和many-to-one
4. JPA关系映射系列四：many-to-many 关联映射
5. JPA关系映射系列五：many-to-many 关联表存在额外字段关系映射