java - 类未在 spring-boot 中实例化(j2EE 到 spring-boot 迁移)

Question

我正在努力将 j2EE 应用程序迁移到 spring-boot..我面临很多挑战..需要您的帮助，以下是我遵循的步骤

1. 是否设置了POM、JAR和WAR打包
2. 尝试将 Servlet 转换为 RestController
3. 我已注册的过滤器

@Configuration

public class FilterConfigService {

    @Bean
    public FilterRegistrationBean mdcFilter() {
        FilterRegistrationBean filterRegBean = new FilterRegistrationBean();
        filterRegBean.setFilter(new MDCFilter());
        filterRegBean.addUrlPatterns("/v2/*");
        filterRegBean.setOrder(1);
        return filterRegBean;
    }

    @Bean
    public FilterRegistrationBean apiOriginFilter() {
        FilterRegistrationBean filterRegBean = new FilterRegistrationBean();
        filterRegBean.setFilter(new ApiOriginFilter());
        filterRegBean.addUrlPatterns("/v2/*");
        filterRegBean.setOrder(2);
        return filterRegBean;
    }
}

有一个单例类，用于通过 servlet 的 Init() 实例化一些必要的东西，我将其删除，因为默认情况下所有 bean 在范围内都是单例，并按如下方式进行实例化(不知道这是否是好的做法)

    @Configuration
    public class PdfExtractServerConfig implements ApplicationListener<ContextRefreshedEvent> {

        @Autowired
        PdfExtractServer pdfExtractServer;

        private static Logger log = Logger.getLogger(PdfExtractServerConfig.class);

        @Override
        public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
            try {
                pdfExtractServer.instance(); // this was called in init of servlet
                System.out.println("instance created ..");
            }
            catch (Throwable e) {
                log.error("Unable to start PdfExtractServer", e);
                throw e;
            }
            //Start monitoring for system health
            ResourceCheck.startMonitoring();
            SplunkMgr.instance().addSplunkMessage("BackPressure", LogLevel.INFO);
        }
    }

单吨类如下所示..

之前是这样

    public static PdfExtractServer instance() {
            if (instance == null) {
                synchronized (startupLock) {
                    if (instance == null) {
                        instance = new PdfExtractServer();
                        instance.start("PES");
                    }
                }
            }
            return instance;
        }

现在我把它做成了

    public static PdfExtractServer instance() {
    //      instance = new PdfExtractServer();
            instance.start("PES");
            return instance;
        }

这是我的测试 Controller

    @RestController
    //@RequestMapping("/")
    public class Test {
        @RequestMapping("/test" )
        public String test(){
            return "Tested OK";
        }
    }

当我尝试运行此渲染时，我不明白我在哪里做错了

Unable to start PdfExtractServer java.lang.NullPointerException at com.it.pes.pdfextract.service.PdfExtractServer.instance(PdfExtractServer.java:78) at com.it.pes.pdfextract.config.PdfExtractServerConfig.onApplicationEvent(PdfExtractServerConfig.java:24) at com.it.pes.pdfextract.config.PdfExtractServerConfig.onApplicationEvent(PdfExtractServerConfig.java:13) at com.it.pes.pdfextract.config.PdfExtractServerConfig$$EnhancerBySpringCGLIB$$e703305a.onApplicationEvent() at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:393) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:347) at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:883) at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.finishRefresh(EmbeddedWebApplicationContext.java:144) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546) at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107)

观察:我尝试通过 glassfish jersey 注册我的过滤器，但在某些 jar 内部，使用了 1.1.1 的 javax.ws.rs-api，因此存在冲突，并且我的应用程序未启动，因此以如上所述的不同方式注册过滤器。

您的帮助对我来说真的是很大的进步..提前致谢..

此处附有包结构。

Answer 1

我同意以上观点。我认为你把事情过于复杂化了。

我相信这就是您所需要的。 @Configuration 注解的类将在服务器启动时运行。 @Bean 注解的方法将被执行一次，并默认创建一个可用于 @Autowire

的单例 bean

所有配置类将首先运行，然后它将扫描所有包并满足服务、组件、存储库、 Controller 。

@Configuration
public class PdfExtractServerConfig {

    @Bean
    public PdfExtractServer pdfExtractServer() {
       final PdfExtractServer pdfExtractServer = new PdfExtractServer();
       pdfExtractServer.start("PES");
       return pdfExtractServer
    }
}

所以当你想在任何其他spring托管bean中使用你的singelton

// Spring will by default scan after this annotation recursively through
// packages on classes and create by default a singleton. It will also 
// search after all bean dependencies that need to be injected. in this case 
// PdfExtracServer and then inject it.
@Component 
public class Foo {

    @Autowire
    private PdfExtractServer pdfExtractServer;

    //different methods here

}