前面我们看完了整个DruidDataSource初始化流程，但是其实Druid除了最核心的数据源之外，还有其他需要自动配置的，细心的人可能看到了，就是利用@Import注解导入的四个类。

DruidFilterConfiguration

public class DruidFilterConfiguration {
    @Bean
    @ConfigurationProperties(FILTER_STAT_PREFIX)
    @ConditionalOnProperty(prefix = FILTER_STAT_PREFIX, name = "enabled")
    @ConditionalOnMissingBean
    public StatFilter statFilter() {
        return new StatFilter();
    }

    @Bean
    @ConfigurationProperties(FILTER_CONFIG_PREFIX)
    @ConditionalOnProperty(prefix = FILTER_CONFIG_PREFIX, name = "enabled")
    @ConditionalOnMissingBean
    public ConfigFilter configFilter() {
        return new ConfigFilter();
    }

    @Bean
    @ConfigurationProperties(FILTER_ENCODING_PREFIX)
    @ConditionalOnProperty(prefix = FILTER_ENCODING_PREFIX, name = "enabled")
    @ConditionalOnMissingBean
    public EncodingConvertFilter encodingConvertFilter() {
        return new EncodingConvertFilter();
    }
    
    \\\\\\\\\\\\\\\\\\\\省略
}

可以看到在某些配置设置的enabled为true的时候会生成对应的bean放到spring容器里面，为后续执行filter做准备。这里如果你项目里面自定义了相同的bean，那么就不会重复创建。

DruidSpringAopConfiguration

@ConditionalOnProperty("spring.datasource.druid.aop-patterns")
public class DruidSpringAopConfiguration {
    @Bean
    public Advice advice() {
        return new DruidStatInterceptor();
    }

    @Bean
    public Advisor advisor(DruidStatProperties properties) {
        return new RegexpMethodPointcutAdvisor(properties.getAopPatterns(), advice());
    }

    @Bean
    @ConditionalOnProperty(name = "spring.aop.auto", havingValue = "false")
    public DefaultAdvisorAutoProxyCreator advisorAutoProxyCreator() {
        DefaultAdvisorAutoProxyCreator advisorAutoProxyCreator = new DefaultAdvisorAutoProxyCreator();
        advisorAutoProxyCreator.setProxyTargetClass(true);
        return advisorAutoProxyCreator;
    }
}

这个是一个AOP的配置，主要实现在DruidStatInterceptor类里面，就是可以监控你用spring.datasource.druid.aop-patterns代表的所有切面，它们里面的方法调用都会被记录。有兴趣的可以去看下它的具体实现。

然后因为是依赖AOP的，如果关闭了AOP会创建一个DefaultAdvisorAutoProxyCreator。

DruidStatViewServletConfiguration

这个是一个监控Servlet的注册，然后可以在spring里面访问。将拿到配置信息，如果有就设置，部分参数会设置默认值。实现如下：

@Bean
    public ServletRegistrationBean statViewServletRegistrationBean(DruidStatProperties properties) {
        DruidStatProperties.StatViewServlet config = properties.getStatViewServlet();
        ServletRegistrationBean registrationBean = new ServletRegistrationBean();
        registrationBean.setServlet(new StatViewServlet());
        registrationBean.addUrlMappings(config.getUrlPattern() != null ? config.getUrlPattern() : "/druid/*");
        if (config.getAllow() != null) {
            registrationBean.addInitParameter("allow", config.getAllow());
        } else {
            registrationBean.addInitParameter("allow", DEFAULT_ALLOW_IP);
        }
        if (config.getDeny() != null) {
            registrationBean.addInitParameter("deny", config.getDeny());
        }
        if (config.getLoginUsername() != null) {
            registrationBean.addInitParameter("loginUsername", config.getLoginUsername());
        }
        if (config.getLoginPassword() != null) {
            registrationBean.addInitParameter("loginPassword", config.getLoginPassword());
        }
        if (config.getResetEnable() != null) {
            registrationBean.addInitParameter("resetEnable", config.getResetEnable());
        }
        return registrationBean;
    }

DruidWebStatFilterConfiguration

@Bean
    public FilterRegistrationBean webStatFilterRegistrationBean(DruidStatProperties properties) {
        DruidStatProperties.WebStatFilter config = properties.getWebStatFilter();
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        WebStatFilter filter = new WebStatFilter();
        registrationBean.setFilter(filter);
        registrationBean.addUrlPatterns(config.getUrlPattern() != null ? config.getUrlPattern() : "/*");
        registrationBean.addInitParameter("exclusions", config.getExclusions() != null ? config.getExclusions() : "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*");
        if (config.getSessionStatEnable() != null) {
            registrationBean.addInitParameter("sessionStatEnable", config.getSessionStatEnable());
        }
        if (config.getSessionStatMaxCount() != null) {
            registrationBean.addInitParameter("sessionStatMaxCount", config.getSessionStatMaxCount());
        }
        if (config.getPrincipalSessionName() != null) {
            registrationBean.addInitParameter("principalSessionName", config.getPrincipalSessionName());
        }
        if (config.getPrincipalCookieName() != null) {
            registrationBean.addInitParameter("principalCookieName", config.getPrincipalCookieName());
        }
        if (config.getProfileEnable() != null) {
            registrationBean.addInitParameter("profileEnable", config.getProfileEnable());
        }
        return registrationBean;
    }

注册Druid的WebStatFilter到spring的filter里面，然后添加一些配置的参数，部分没有设置的会给默认值。

总结

这四个组件其实大部分都是填充值，里面需要注意的是DruidSpringAopConfiguration，这里面有个DruidStatInterceptor类的实现其实东西不少，但是它是在com.alibaba.druid.support.spring包下的，不在这次druid-spring-boot-starter范围内，后面看到会记录一下的。