CommandLineRunner和Application怎么使用

这篇文章主要讲解了"CommandLineRunner和Application怎么使用"，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习"CommandLineRunner和Application怎么使用"吧！

应用启动数据初始化接口CommandLineRunner和Application详解

在SpringBoot项目中创建组件类实现CommandLineRunner或ApplicationRunner接口可实现在应用启动之后及时进行一些初始化操作，如缓存预热、索引重建等等类似一些数据初始化操作。

两个接口功能相同，都有个run方法需要重写，只是实现方法的参数不同。

CommandLineRunner接收原始的命令行启动参数，ApplicationRunner则将启动参数对象化。

1 运行时机

两个接口都是在SpringBoot应用初始化好上下文之后运行，所以在运行过程中，可以使用上下文中的所有信息，例如一些Bean等等。在框架SpringApplication类源码的run方法中，可查看Runner的调用时机callRunners，如下：

/** * Run the Spring application, creating and refreshing a new * {@link ApplicationContext}. * @param args the application arguments (usually passed from a Java main method) * @return a running {@link ApplicationContext} */public ConfigurableApplicationContext run(String... args) {        StopWatch stopWatch = new StopWatch();        stopWatch.start();        ConfigurableApplicationContext context = null;        Collection exceptionReporters = new ArrayList<>();        configureHeadlessProperty();        SpringApplicationRunListeners listeners = getRunListeners(args);        listeners.starting();        try {                ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);                ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);                configureIgnoreBeanInfo(environment);                Banner printedBanner = printBanner(environment);                context = createApplicationContext();                exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,                                new Class[] { ConfigurableApplicationContext.class }, context);                prepareContext(context, environment, listeners, applicationArguments, printedBanner);                refreshContext(context);                afterRefresh(context, applicationArguments);                stopWatch.stop();                if (this.logStartupInfo) {                        new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);                }                listeners.started(context);                //调用Runner，执行初始化操作                callRunners(context, applicationArguments);        }        catch (Throwable ex) {                handleRunFailure(context, ex, exceptionReporters, listeners);                throw new IllegalStateException(ex);        }        try {                listeners.running(context);        }        catch (Throwable ex) {                handleRunFailure(context, ex, exceptionReporters, null);                throw new IllegalStateException(ex);        }        return context;}

2 实现接口

2.1 CommandLineRunner

简单实现如下，打印启动参数信息：

@Order(1)@Componentpublic class CommandLineRunnerInit implements CommandLineRunner {    private Logger logger = LoggerFactory.getLogger(this.getClass());    private final String LOG_PREFIX = ">>>>>>>>>>CommandLineRunner >>>>>>>>>> ";    @Override    public void run(String... args) throws Exception {        try {            this.logger.error("{} args:{}", LOG_PREFIX, StringUtils.join(args, ","));        } catch (Exception e) {            logger.error("CommandLineRunnerInit run failed", e);        }    }}

2.2 ApplicationRunner

简单实现如下，打印启动参数信息，并调用Bean的方法（查询用户数量）：

@Order(2)@Componentpublic class ApplicationRunnerInit implements ApplicationRunner {    private Logger logger = LoggerFactory.getLogger(this.getClass());    private final String LOG_PREFIX = ">>>>>>>>>>ApplicationRunner >>>>>>>>>> ";    private final UserRepository userRepository;    public ApplicationRunnerInit(UserRepository userRepository) {        this.userRepository = userRepository;    }    @Override    public void run(ApplicationArguments args) throws Exception {        try {            this.logger.error("{} args:{}", LOG_PREFIX, JSONObject.toJSONString(args));            for (String optionName : args.getOptionNames()) {                this.logger.error("{} argName:{} argValue:{}", LOG_PREFIX, optionName, args.getOptionValues(optionName));            }            this.logger.error("{} user count:{}", LOG_PREFIX, this.userRepository.count());        } catch (Exception e) {            logger.error("CommandLineRunnerInit run failed", e);        }    }}

3 执行顺序

如果实现了多个Runner，默认会按照添加顺序先执行ApplicationRunner的实现再执行CommandLineRunner的实现，如果多个Runner之间的初始化逻辑有先后顺序，可在实现类添加@Order注解设置执行顺序，可在源码SpringApplication类的callRunners方法中查看，如下：

private void callRunners(ApplicationContext context, ApplicationArguments args) { List