spring boot starter开发

作为公司的技术保障部，一直承担着技术方向的把控，最近公司准备全面转入spring boot的开发。所以我们部门也一直在调研相关的技术知识点；

使用springboot开发应用已经有一段时间了，我们都沉醉于它简洁的配置和平滑的上手曲线。

在springboot的开发中，starter是一个核心的配置，只需要引入对应模块的starter，然后在application.properties中引入对应的配置项，就可以开发业务逻辑了。

这一切都归功于springboot的自动配置的能力。

本文会从一个mybatis与spring boot结合的starter开始学习，该框架是我们提供出来，需要使用mybatis的团队只需要引入这个starter的jar包即可使用

新建原型项目

完整的pom.xml如下

<?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>

    <parent>
        <groupId>cn.caijiajia</groupId>
        <artifactId>springboot-parent</artifactId>
        <version>1.0.0.RELEASE</version>
    </parent>

    <groupId>cn.caijiajia</groupId>
    <artifactId>mybatis-starter</artifactId>
    <version>${project.release.version}</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>cn.caijiajia</groupId>
            <artifactId>framework-starter</artifactId>
            <version>${project.release.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
        </dependency>

        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>tomcat-jdbc</artifactId>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
        </dependency>

        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
    </dependencies>

</project>

开发阶段

1.配置类 DatabaseAutoConfiguration DbProperties

@EnableConfigurationProperties({DbProperties.class})
public class DatabaseAutoConfiguration
        implements BeanDefinitionRegistryPostProcessor, EnvironmentAware {

    private static Logger log = LoggerFactory.getLogger(DatabaseAutoConfiguration.class);

    private Environment environment;

    @Override
    public void setEnvironment(Environment environment) {
        this.environment = environment;
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    }

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        DbProperties dbProperties = ConfigUtil.getDbConfig(environment, DbProperties.PROPERTY_PREFIX,
                DbProperties.class);
        // TODO 检查参数
        if (dbProperties.getDatabase() == null && dbProperties.getDatabases() != null && dbProperties
                .getDatabases().size() == 1) {
            dbProperties.setDatabase(dbProperties.getDatabases().get(0));
        }
        initAllDataAccessBean(dbProperties, registry);
    }

    protected void initAllDataAccessBean(DbProperties dbProperties, BeanDefinitionRegistry registry) {
        // 单数据源
        if (dbProperties.getDatabase() != null) {
            initDataAccessBean(dbProperties.getDatabase(), null, registry);
        }
        // 多数据源
        else if (dbProperties.getDatabases() != null && dbProperties.getDatabases().size() > 0) {
            for (int i = 0; i < dbProperties.getDatabases().size(); i++) {
                initDataAccessBean(dbProperties.getDatabases().get(i), i, registry);
            }
        }
    }

    /**
     * 注册一个datasource的所有bean 信息
     *
     * @param databaseConfig
     * @param index
     * @param registry
     */
    protected void initDataAccessBean(DatabaseConfig databaseConfig, Integer index, BeanDefinitionRegistry registry) {
        DataSourceConfig dataSourceConfig = databaseConfig.getDataSource();
        TransactionConfig transactionConfig = databaseConfig.getTransaction();
        MyBatisConfig myBatisConfig = databaseConfig.getMybatis();
        LogConfig logConfig = databaseConfig.getLog();

        // 给与默认 dataSource bean id: dataSource${index}
        if (StringUtils.isEmpty(dataSourceConfig.getName())) {
            if (index == null) {
                dataSourceConfig.setName("dataSource");
            } else {
                dataSourceConfig.setName("dataSource" + index);
            }
        }

        // 注册datasource
        registry.registerBeanDefinition(dataSourceConfig
                .getName(), getTomcatJdbcDataSourceBeanDefinition(dataSourceConfig, logConfig));

        // 注册事务
        if (transactionConfig != null && transactionConfig.isEnable()) {
            if (index == null) {
                registry.registerBeanDefinition("transactionManager", getTransactionManagerBeanDefinition(dataSourceConfig));
            } else {
                registry.registerBeanDefinition("transactionManager" + index, getTransactionManagerBeanDefinition(dataSourceConfig));
            }
        }

        // 注册mybatis
        if (myBatisConfig != null) {
            final String sqlSessionFactoryBeanName = "sqlSessionFactory" + dataSourceConfig.getName();
            registry.registerBeanDefinition(sqlSessionFactoryBeanName, getSqlSessionFactoryBeanDefinition(myBatisConfig, dataSourceConfig));
            registry.registerBeanDefinition("mapperScannerConfigurer" + dataSourceConfig
                    .getName(), getMapperScannerConfigurerBeanDefinition(myBatisConfig, sqlSessionFactoryBeanName));

            // 给与默认 dataSource bean id: sqlSession${index}
            if (StringUtils.isEmpty(myBatisConfig.getSqlSessionBeanName())) {
                if (index == null) {
                    myBatisConfig.setSqlSessionBeanName("sqlSession");
                } else {
                    myBatisConfig.setSqlSessionBeanName("sqlSession" + index);
                }
            }
            registry.registerBeanDefinition(myBatisConfig
                    .getSqlSessionBeanName(), getSqlSessionBeanDefinition(sqlSessionFactoryBeanName));
        }
    }

    /**
     * 获取 tomcat jdbc datasource bean 定义
     *
     * @param dataSourceConfig
     * @return
     */
    protected AbstractBeanDefinition getTomcatJdbcDataSourceBeanDefinition(DataSourceConfig dataSourceConfig, LogConfig logConfig) {
        if (dataSourceConfig.getMinIdle() == null) {
            dataSourceConfig.setMinIdle(dataSourceConfig.getInitialSize());
        }
        if (dataSourceConfig.getMaxIdle() == null) {
            dataSourceConfig.setMaxIdle(dataSourceConfig.getMaxActive());
        }

        BeanDefinitionBuilder definitionBuilder = BeanDefinitionBuilder
                .rootBeanDefinition("org.apache.tomcat.jdbc.pool.DataSource");
        definitionBuilder.setDestroyMethodName("close");

        // add filter
        definitionBuilder
                .addPropertyValue("jdbcInterceptors", "cn.caijiajia.framework.db.log.TomcatJdbcLogFilter(slowLogOn=" + logConfig
                        .isSlowSqlOn() + ",slowSqlThreshold=" + logConfig.getSlowSqlThreshold() + ")");

        // if not set, use default value in jdbc driver
        if (dataSourceConfig.getDefaultAutoCommit() != null) {
            definitionBuilder
                    .addPropertyValue("defaultAutoCommit", dataSourceConfig.getDefaultAutoCommit());
        }
        if (dataSourceConfig.getDefaultReadOnly() != null) {
            definitionBuilder
                    .addPropertyValue("defaultReadOnly", dataSourceConfig.getDefaultReadOnly());
        }
        if (dataSourceConfig.getDefaultTransactionIsolation() != null) {
            definitionBuilder
                    .addPropertyValue("defaultTransactionIsolation", dataSourceConfig.getDefaultTransactionIsolation());
        }

        definitionBuilder.addPropertyValue("url", dataSourceConfig.getUrl());
        definitionBuilder.addPropertyValue("username", dataSourceConfig.getUsername());
        definitionBuilder.addPropertyValue("password", dataSourceConfig.getPassword());
        definitionBuilder.addPropertyValue("driverClassName", dataSourceConfig.getDriverClassName());

        // 配置初始化大小、最小、最大
        definitionBuilder.addPropertyValue("initialSize", dataSourceConfig.getInitialSize());
        definitionBuilder.addPropertyValue("minIdle", dataSourceConfig.getMinIdle());
        definitionBuilder.addPropertyValue("maxActive", dataSourceConfig.getMaxActive());
        definitionBuilder.addPropertyValue("maxIdle", dataSourceConfig.getMaxIdle());

        // 配置获取连接等待超时的时间
        definitionBuilder.addPropertyValue("maxWait", dataSourceConfig.getMaxWait());
        // 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫
        definitionBuilder
                .addPropertyValue("timeBetweenEvictionRunsMillis", dataSourceConfig.getTimeBetweenEvictionRunsMillis());
        // 配置一个连接在池中最小生存的时间，单位是毫秒
        definitionBuilder
                .addPropertyValue("minEvictableIdleTimeMillis", dataSourceConfig.getMinEvictableIdleTimeMillis());

        definitionBuilder.addPropertyValue("validationQuery", "select 1");
        definitionBuilder.addPropertyValue("testOnConnect", dataSourceConfig.isTestOnConnect());
        definitionBuilder.addPropertyValue("testWhileIdle", dataSourceConfig.isTestWhileIdle());
        definitionBuilder.addPropertyValue("testOnBorrow", dataSourceConfig.isTestOnBorrow());
        definitionBuilder.addPropertyValue("testOnReturn", dataSourceConfig.isTestOnReturn());

        definitionBuilder.addPropertyValue("removeAbandoned", dataSourceConfig.isRemoveAbandoned());
        definitionBuilder.addPropertyValue("removeAbandonedTimeout", dataSourceConfig.getRemoveAbandonedTimeout());

        AbstractBeanDefinition bd = definitionBuilder.getRawBeanDefinition();
        bd.setScope(BeanDefinition.SCOPE_SINGLETON);

        return bd;
    }

    /**
     * 获取mybaits SqlSessionFactory bean 定义
     *
     * @param dataSourceConfig
     * @return
     */
    protected AbstractBeanDefinition getSqlSessionFactoryBeanDefinition(MyBatisConfig myBatisConfig, DataSourceConfig dataSourceConfig) {
        BeanDefinitionBuilder definitionBuilder = BeanDefinitionBuilder
                .rootBeanDefinition(org.mybatis.spring.SqlSessionFactoryBean.class);
        definitionBuilder.addPropertyReference("dataSource", dataSourceConfig.getName());

        PageInterceptor pageInterceptor = new PageInterceptor();
        if (myBatisConfig.getPage().isSupportMethodsArguments()) {
            Properties pageInterceptorProperties = new Properties();
            pageInterceptorProperties.setProperty("supportMethodsArguments", "true");
            pageInterceptorProperties.setProperty("params", "pageNum=pageNum;pageSize=pageSize");
            pageInterceptor.setProperties(pageInterceptorProperties);
        }

        definitionBuilder
                .addPropertyValue("plugins", new Interceptor[]{new LogInfoInterceptor(), pageInterceptor});

        AbstractBeanDefinition bd = definitionBuilder.getRawBeanDefinition();
        bd.setScope(BeanDefinition.SCOPE_SINGLETON);

        return bd;
    }

    /**
     * 获取mybaits MapperScannerConfigurer bean 定义
     *
     * @param myBatisConfig
     * @param sqlSessionFactoryBeanName
     * @return
     */
    protected AbstractBeanDefinition getMapperScannerConfigurerBeanDefinition(MyBatisConfig myBatisConfig, String sqlSessionFactoryBeanName) {
        BeanDefinitionBuilder definitionBuilder = BeanDefinitionBuilder
                .rootBeanDefinition(org.mybatis.spring.mapper.MapperScannerConfigurer.class);
        definitionBuilder
                .addPropertyValue("sqlSessionFactoryBeanName", sqlSessionFactoryBeanName);
        definitionBuilder.addPropertyValue("basePackage", myBatisConfig.getBasePackage());

        AbstractBeanDefinition bd = definitionBuilder.getRawBeanDefinition();
        bd.setScope(BeanDefinition.SCOPE_SINGLETON);

        return bd;
    }

    /**
     * 获取mybaits SqlSessionTemplate bean 定义
     *
     * @param sqlSessionFactoryBeanName
     * @return
     */
    protected AbstractBeanDefinition getSqlSessionBeanDefinition(String sqlSessionFactoryBeanName) {
        BeanDefinitionBuilder definitionBuilder = BeanDefinitionBuilder
                .rootBeanDefinition(org.mybatis.spring.SqlSessionTemplate.class);
        definitionBuilder.addConstructorArgReference(sqlSessionFactoryBeanName);
        AbstractBeanDefinition bd = definitionBuilder.getRawBeanDefinition();
        bd.setScope(BeanDefinition.SCOPE_SINGLETON);

        return bd;
    }

    /**
     * 获取 DataSourceTransactionManager bean定义
     *
     * @param dataSourceConfig
     * @return
     */
    protected AbstractBeanDefinition getTransactionManagerBeanDefinition(DataSourceConfig dataSourceConfig) {
        BeanDefinitionBuilder definitionBuilder = BeanDefinitionBuilder
                .genericBeanDefinition(DataSourceTransactionManager.class);
        definitionBuilder.addConstructorArgReference(dataSourceConfig.getName());
        AbstractBeanDefinition bd = definitionBuilder.getRawBeanDefinition();
        bd.setScope(BeanDefinition.SCOPE_SINGLETON);

        return bd;
    }
}

　　

@ConfigurationProperties(prefix = DbProperties.PROPERTY_PREFIX)
public class DbProperties {

    public final static String PROPERTY_PREFIX = "caijiajia.db";

    private DatabaseConfig database;

    private List<DatabaseConfig> databases = new ArrayList();

    public DatabaseConfig getDatabase() {
        return database;
    }

    public void setDatabase(DatabaseConfig database) {
        this.database = database;
    }

    public List<DatabaseConfig> getDatabases() {
        return databases;
    }

    public void setDatabases(List<DatabaseConfig> databases) {
        this.databases = databases;
    }
}

　　

这是两段核心配置类，其它还有一些pojo类，这里就不写出来了

自定义spring.factories

自定义spring.factories的步骤很简单，只需要在src/main/resource目录下创建META-INF目录,并在该目录下添加文件spring.factories，文件内容为：

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
cn.caijiajia.framework.db.autoconfigure.DatabaseAutoConfiguration　　

到这里通过spring boot的自动装配原理实现了配置类的自动装配

一个简单的starter创造就完成了