Master SpringBoot 2.7: Access Params, Banner, Converters, and Graceful Shutdown

1. Application Parameters

SpringBoot can receive startup arguments such as:

<code>java -jar app.jar --pack.title=xxx --pack.version=1.0.0</code>

These arguments can be accessed via Environment :

<code>@Resource
private Environment env;
public void getArgs() {
  String title = env.getProperty("pack.title");
  String version = env.getProperty("pack.version");
}</code>

SpringBoot also registers an ApplicationArguments bean that can be injected directly:

<code>@Resource
private ApplicationArguments applicationArguments;
public void getArgs() {
  List&lt;String&gt; titles = applicationArguments.getOptionValues("pack.title");
  List&lt;String&gt; versions = applicationArguments.getOptionValues("pack.version");
}</code>

You can obtain the raw argument array:

<code>String[] args = applicationArguments.getSourceArgs();</code>

Output example:

<code>[--pack.title=xxx, --pack.version=1.0.0]</code>

2. Banner

Inject the Banner bean to print the banner programmatically:

<code>@Resource
private Banner banner;
@Resource
private Environment env;
public void printBanner() {
  banner.printBanner(env, PackApplication.class, System.out);
}</code>

Ensure the banner is not disabled (no spring.main.banner-mode: off configuration) or the injection will fail. It can also be disabled programmatically:

<code>SpringApplication app = new SpringApplication(PackApplication.class);
app.setBannerMode(Mode.OFF);
</code>

3. Type Converters

The ConversionService converts configuration values and request parameters:

<code>@Resource
private ConversionService conversionService;
Integer ret = conversionService.convert("6666",
  TypeDescriptor.valueOf(String.class),
  TypeDescriptor.valueOf(Integer.class));</code>

Custom converters can be registered via WebMvcConfigurer :

<code>@Configuration
public class WebConfig implements WebMvcConfigurer {
  @Override
  public void addFormatters(FormatterRegistry registry) {
    registry.addConverterFactory(new ConverterFactory&lt;String, User&gt;() {
      @Override
      public &lt;T extends User&gt; Converter&lt;String, T&gt; getConverter(Class&lt;T&gt; targetType) {
        return source -> {
          String[] s = source.split(",");
          return (T) new User(Integer.valueOf(s[0]), s[1]);
        };
      }
    });
  }
}
</code>

4. Servlet‑Related Beans

SpringBoot registers the following servlet‑related beans that can be injected safely:

ServletRequest

ServletResponse

HttpSession

WebRequest

These beans are backed by ObjectFactory and retrieve the actual request/response from a ThreadLocal:

<code>@Resource
private HttpServletRequest request;
@Resource
private HttpServletResponse response;
public void getParam() {
  String value = request.getParameter("name");
}</code>

5. Internationalization (MessageSource)

Inject MessageSource to obtain localized messages:

<code>@Resource
private MessageSource messageSource;
public void getMsg() {
  String message = messageSource.getMessage(
    "pack.info.message",
    new Object[]{"张三"},
    "我是默认消息",
    Locale.CHINA);
}</code>

If no default message is provided, Spring uses DelegatingMessageSource , which is empty. Configure the base name in application.yml to enable i18n:

<code>spring:
  messages:
    basename: i18n/message</code>

SpringBoot then registers a ResourceBundleMessageSource . Alternatively, you can inject ConfigurableApplicationContext and call getMessage , which internally uses the same MessageSource :

<code>@Resource
private ConfigurableApplicationContext context;
String message = context.getMessage(
  "pack.info.message",
  new Object[]{"张三"},
  "我是默认消息",
  Locale.CHINA);
</code>

6. Event Publishing

Publish events via the application context:

<code>@Resource
private ConfigurableApplicationContext context;
context.publishEvent(new TxApplicationEvent(context));
</code>

Spring also registers an ApplicationEventMulticaster bean for broadcasting events:

<code>@Resource
private ApplicationEventMulticaster eventMulticast;
eventMulticast.multicastEvent(new TxApplicationEvent(context));
</code>

You can provide a custom bean named applicationEventMulticaster to replace the default implementation.

7. Graceful Shutdown

When running an embedded Tomcat jar, SpringBoot registers WebServerGracefulShutdownLifecycle to allow graceful shutdown:

<code>@Resource
private WebServerGracefulShutdownLifecycle webServerGracefulShutdown;
public void shutdownWebServer() {
  webServerGracefulShutdown.stop(() -> {
    System.out.println("Gracefully shutting down Web Server");
    context.close();
  });
}
</code>

Enable graceful shutdown in configuration:

<code>server:
  shutdown: graceful</code>

After invoking the shutdown, the console prints the message shown below.