使用Spring Boot快速构建基于SQLite数据源的应用

为了提供一个单包易部署的服务器应用，考虑使用Spring Boot，因为其集成了Apache Tomcat，易于运行，免去绝大部分了服务器配置的步骤。

项目初始化

首先从mvn archetype:generate中选择 com.github.mkspcd:simple-webapp(或其他webapp模版) 模版生成项目结构。

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在pom.xml中添加parent来获取Spring Boot所需的最小依赖。

<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/maven-v4_0_0.xsd">    <modelVersion>4.0.0</modelVersion>    <groupId>com.github.hwding.example</groupId>    <artifactId>example</artifactId>    <packaging>jar</packaging>    <version>0.0.1</version>    <name>an example</name>    <url>https://github.com/hwding</url>    <!-- 添加Spring的Repository以便于添加相关组件 -->    <repositories>        <repository>            <url>http://repo.spring.io/milestone/</url>            <id>repo-spring</id>        </repository>    </repositories>    <parent>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-parent</artifactId>        <version>1.5.6.RELEASE</version>    </parent>    <build>        <finalName>example</finalName>        <plugins>            <plugin>                <groupId>org.springframework.boot</groupId>                <artifactId>spring-boot-maven-plugin</artifactId>            </plugin>            <!-- 编译级别，可选 -->            <plugin>                <groupId>org.apache.maven.plugins</groupId>                <artifactId>maven-compiler-plugin</artifactId>                <configuration>                    <source>1.8</source>                    <target>1.8</target>                </configuration>            </plugin>        </plugins>    </build>    <dependencies>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-data-jpa</artifactId>        </dependency>        <!-- 用于Hibernate4的SQLite3 Dialect -->        <dependency>            <groupId>com.enigmabridge</groupId>            <artifactId>hibernate4-sqlite-dialect</artifactId>            <version>0.1.2</version>        </dependency>        <!-- 用于配置数据源 -->        <dependency>            <groupId>org.apache.commons</groupId>            <artifactId>commons-dbcp2</artifactId>            <version>2.1.1</version>        </dependency>        <dependency>            <groupId>org.eclipse.persistence</groupId>            <artifactId>javax.persistence</artifactId>            <version>2.2.0-RC1</version>        </dependency>        <!-- SQLite3 驱动 -->        <dependency>            <groupId>org.xerial</groupId>            <artifactId>sqlite-jdbc</artifactId>            <version>3.20.0</version>        </dependency>    </dependencies></project>

pom中同时添加了Hibernate以及Spring JPA等相关组件。

配置数据源

@Configurationpublic class DataSourceConfiguration {    @Bean(destroyMethod = "", name = "EmbeddeddataSource")    public DataSource dataSource() {        DataSourceBuilder dataSourceBuilder = DataSourceBuilder.create();        dataSourceBuilder.driverClassName("org.sqlite.JDBC");        dataSourceBuilder.url("jdbc:sqlite:" + "example.db");        dataSourceBuilder.type(SQLiteDataSource.class);        return dataSourceBuilder.build();    }}

这里设置了该Bean的destroyMethod = ""是为了防止停止服务器时容器管理器两次销毁导致的异常，name = "EmbeddeddataSource"用于在自动装配Bean时与其他dataSource加以区分。

为了使该独立服务易部署易分发，使用SQLite3作为数据存取的源，值得注意的是，该场景非常少见。

配置Spring Data JPA

@Configuration@EnableJpaRepositories(        basePackages = "com.github.hwding.example.data.repository",        transactionManagerRef = "jpaTransactionManager",        entityManagerFactoryRef = "localContainerEntityManagerFactoryBean")@EnableTransactionManagementpublic class JpaConfiguration {    @Autowired    @Bean    public JpaTransactionManager jpaTransactionManager(@Qualifier(value = "EmbeddeddataSource") DataSource dataSource, EntityManagerFactory entityManagerFactory) {        JpaTransactionManager jpaTransactionManager                = new JpaTransactionManager();        jpaTransactionManager.setEntityManagerFactory(entityManagerFactory);        jpaTransactionManager.setDataSource(dataSource);        return jpaTransactionManager;    }    @Autowired    @Bean    LocalContainerEntityManagerFactoryBean localContainerEntityManagerFactoryBean(@Qualifier(value = "EmbeddeddataSource") DataSource dataSource, JpaVendorAdapter jpaVendorAdapter) {        LocalContainerEntityManagerFactoryBean localContainerEntityManagerFactoryBean                = new LocalContainerEntityManagerFactoryBean();        localContainerEntityManagerFactoryBean.setDataSource(dataSource);        localContainerEntityManagerFactoryBean.setPackagesToScan("com.github.hwding.example.data.model.local");        localContainerEntityManagerFactoryBean.setJpaVendorAdapter(jpaVendorAdapter);        return localContainerEntityManagerFactoryBean;    }    @Bean    public JpaVendorAdapter jpaVendorAdapter() {        HibernateJpaVendorAdapter hibernateJpaVendorAdapter = new HibernateJpaVendorAdapter();        hibernateJpaVendorAdapter.setGenerateDdl(true);        hibernateJpaVendorAdapter.setShowSql(true);        hibernateJpaVendorAdapter.setDatabasePlatform("com.enigmabridge.hibernate.dialect.SQLiteDialect");        return hibernateJpaVendorAdapter;    }}

注意Repository和Entity扫描的包路径需要根据实际进行调整。

hibernateJpaVendorAdapter.setGenerateDdl(true);能够在初次运行时自动根据Entity的定义生成DDL并自动创建SQLite3的.db 数据文件，在本例中是 example.db ，DDL会最小程度的满足Entity的定义；如果该文件已经存在，则并不会对其进行覆盖。

由于Hibernate并不对SQLite3提供支持，所以需要提供第三方Dialect给它：hibernateJpaVendorAdapter.setDatabasePlatform("com.enigmabridge.hibernate.dialect.SQLiteDialect");，这个类我们已经在pom中引入了。

配置入口

@SpringBootApplicationpublic class Application {    public static void main(String[] args) {        SpringApplication.run(Application.class);    }}

Spring Boot能够从JAR包的入口直接启动整个应用程序。