java - Spring 启动: "Error creating bean with name baseConfig: Invocation of init method failed" NPE

Question

我看到运行应用程序时抛出 NullPointerException。更具体地说，我的一个配置类导致了 NullPointerException，我不确定为什么会发生这种情况。

我只是尝试在 Controller 中 Autowiring 配置类，以便我可以查看属性值是否已正确填充:

@RestController
public class ApplicationController {

    @Autowired
    private TopicConsumerConfig topicConsumerConfig;

    @RequestMapping("/")
    public String showConfigs() {
        return topicConsumerConfig.toString();
    }
}

以下是有问题的类:

@Component
@ConfigurationProperties
public class BaseConfig {

    Properties props;
    private String username;
    private String hostname;

    public Properties getProps() {
        return props;
    }
    public void setProps(Properties props) {
        this.props = props;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getHostname() {
        return hostname;
    }
    public void setHostname(String hostname) {
        this.hostname = hostname;
    }

    @PostConstruct
    public void loadProperties() {
        props = new Properties();

        props.setProperty("hostname", this.hostname);
        props.setProperty("username", this.username);
    }

}


@Component
@ConfigurationProperties
public class ConsumerConfig extends BaseConfig {

    private String password;

    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "ConsumerConfig [hostname=" + getHostname() + ", username=" + getUsername() + ", password=" + password + "]";
    }

    @Override
    @PostConstruct
    public void loadProperties() {
        super.loadProperties();

        props.setProperty("password", this.password);
    }
}

@Configuration
@PropertySource(
        value = "classpath:consumer.properties",
        ignoreResourceNotFound=false
        )
@ConfigurationProperties(prefix="com.training.consumer")
public class TopicConsumerConfig extends ConsumerConfig {

}

消费者属性:

com.training.consumer.hostname=myhost
com.training.consumer.username=myusername
com.training.consumer.password=mypassword

我收到的错误如下:

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2018-12-16 22:10:50.428 ERROR 2010 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'baseConfig': Invocation of init method failed; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:139) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:419) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1737) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:576) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:498) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:846) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:863) ~[spring-context-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546) ~[spring-context-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at com.example.demo.VismarkApplication.main(VismarkApplication.java:10) [classes/:na]
Caused by: java.lang.NullPointerException: null
    at java.util.Hashtable.put(Hashtable.java:460) ~[na:1.8.0_181]
    at java.util.Properties.setProperty(Properties.java:166) ~[na:1.8.0_181]
    at com.example.demo.config.BaseConfig.loadProperties(BaseConfig.java:41) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_181]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:363) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:307) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:136) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    ... 18 common frames omitted

我哪里出错了？

Answer 1

因为您的 Consumer.properties 中有以下内容

com.training.consumer.hostname=myhost 
com.training.consumer.username=myusername 
com.training.consumer.password=mypassword

但是您的BaseConfig 只有变量用户名、密码，属性未正确映射。更改您的 @ConfigurationProperties 以具有如下前缀属性。

@ConfigurationProperties(prefix="com.training.consumer")