java - 运行从 springboot 项目打包的 jar 时无法获取 bean

Question

我可以在 IDEA 中很好地运行我的 springboot 项目，但是当将它打包到一个 jar 并使用 java 命令运行时，从 spring 上下文获取 bean 时只得到 java.lang.NullPointerException。

刚出错的第一个类:

@Service
public class MdspiImpl extends CThostFtdcMdSpi {
public MdspiImpl(CThostFtdcMdApi mdapi) {
        m_mdapi = mdapi;
        logger.info("MdspiImpl is creating...");
        ***mdr = SpringContextUtil.getBean("marketDataRobot");//this is the error code***
    }
}

第二类:

@Service
public class MarketDataRobot {
}

SpringContextUtil 类:

@Component("SpringContextUtil")
public class SpringContextUtil implements ApplicationContextAware {
    private static ApplicationContext applicationContext;
    public static <T> T getBean(String name) {
        return (T) applicationContext.getBean(name);
    }
}

gradle文件:

jar {
    baseName = 'programmingTrading'
    version =  '0.1.0'
    manifest {
        attributes 'Main-Class': 'com.blackHole.programmingTrading'
    }
}

运行异常:

WARN main[AbstractApplicationContext.java:557 Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mdspiImpl' defined in URL [jar:file:/E:/workspace/simuPrd/programmingTrading-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/com/blackHole/programmingTrading/infrastructure/MdspiImpl.class]: Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.blackHole.programmingTrading.infrastructure.MdspiImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException] 
[com.blackHole.programmingTrading.infrastructure.MdspiImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:184)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:117)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:300)
    ... 27 common frames omitted
Caused by: java.lang.NullPointerException: null
    at com.blackHole.programmingTrading.SpringContextUtil.getBean(SpringContextUtil.java:35)
    at com.blackHole.programmingTrading.infrastructure.MdspiImpl.<init>(MdspiImpl.java:46)

它也源于另一个问题:@Autowired 注释不起作用...像这样使用时:

@Component
public class Scu{
}

在另一个类中:

@Autowired
private Scu scu;
logger.info(String.format("MdspiImpl is creating...[%s]", scu.toString()));

将得到一个 java.lang.NullPointerException: null

spring-boot 配置如下:

@SpringBootApplication
public class ProgrammingTrading {
    public static void main(String[] args) {
        SpringApplication.run(ProgrammingTrading.class, args);
    }
}

这是使用 SpringContextUtil 获取 bean 的部分原因...非常感谢!

Answer 1

SpringContextUtil 不应像您正在做的那样静态访问...因为您将其定义为 @Component，请执行以下操作；

@Service
public class MdspiImpl extends CThostFtdcMdSpi {

    @Autowired
    private SpringContextUtil springContextUtil;

    public MdspiImpl(CThostFtdcMdApi mdapi) {
        m_mdapi = mdapi;
        logger.info("MdspiImpl is creating...");
        ***mdr = springContextUtil.getBean("marketDataRobot");
    }
}

由于 SpringContextUtil 不是通过 Spring 注入(inject)的，而是简单地静态访问的，因此其中的 applicationContext 将被忽略，在您的情况下为 null。

同时去掉static修饰符；

@Component
public class SpringContextUtil implements ApplicationContextAware {

    private ApplicationContext applicationContext;

    // include getter/setter for applicationContext as well

    public <T> T getBean(String name) {
        return (T) applicationContext.getBean(name);
    }
}

编辑

最新示例项目的问题；

@Service
public class ExampleService {
    @Autowired
    private Logger logger;

    public ExampleService() {
        this.logger=logger;
        logger.info("Im working");
    }
}

这里 Logger 将为 null，当 ExampleService 构造函数被触发时，因为构造函数在注入(inject)开始之前被调用，但是如果合并，则可以合并此行为通过上述构造函数注入(inject)如下；

@Service
public class ExampleService {

    private final Logger logger;

    public ExampleService(Logger logger) {
        this.logger = logger;
        logger.info("Im working");
    }
}

完美运行，没有任何问题......