java - 如何解决我的 Spring 应用程序中的此异常？

Question

这是我的配置文件

import java.util.Properties;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.orm.hibernate5.HibernateTemplate;
import org.springframework.orm.hibernate5.HibernateTransactionManager;
import org.springframework.orm.hibernate5.LocalSessionFactoryBean;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

@Configuration
//activates spring MVC
@EnableWebMvc
//scans for our classes in the package
@ComponentScan("in.nit")
//loads properties file into Spring Container
@PropertySource("classpath:app.properties")

public class AppConfig {
@Autowired
Environment env;

//1.DataSource
@Bean
public DataSource ds() {
    BasicDataSource ds = new BasicDataSource();
    ds.setDriverClassName(env.getProperty("db.driver"));
    ds.setUrl("db.url");
    ds.setUsername("db.user");
    ds.setPassword("db.password");
    return ds;
}
//session factory
@Bean
public LocalSessionFactoryBean sf() {
    LocalSessionFactoryBean sf = new LocalSessionFactoryBean();
    sf.setDataSource(ds());
    sf.setHibernateProperties(props());
//  sf.setAnnotatedClasses(annotatedClasses);
    sf.setPackagesToScan("in.nit.model");
    return  sf;
}
//Hibernate properties

public Properties props() {
    Properties props = new Properties();
    props.put("hibernate.dialect", env.getProperty("orm.dialect"));
    props.put("hibernate.format_sql",env.getProperty("orm.format_sql"));
    props.put("hibernate.show_sql",env.getProperty("orm.show_sql"));
    props.put("hibernate.hbm2ddl.auto", env.getProperty("orm.hb2ddl.auto"));
    return props;

}
//Tx Manager

@Bean
public HibernateTransactionManager tm() {
    HibernateTransactionManager tm = new HibernateTransactionManager();
    tm.setSessionFactory(sf().getObject());
    return tm;
}
//HibernateTemplate
@Bean
public HibernateTemplate ht() {
    HibernateTemplate ht = new HibernateTemplate();
    ht.setSessionFactory(sf().getObject());
    return ht;
}

//view resolver
@Bean
public InternalResourceViewResolver vr() {
    InternalResourceViewResolver vr = new InternalResourceViewResolver();
    vr.setSuffix(env.getProperty("mvc.suffix"));
    vr.setPrefix(env.getProperty("mvc.prefix"));
    return vr;
}
}

这是我的属性文件，配置将从中读取值

##Connection Properties##
db.driver = oracle.jdbc.driver.OracleDriver
db.url = jdbc:oracle:thin:@localhost:1521:ORCL.168.0.29
db.user = prem
db.password = rempe


##ORM PROPERTIES ##
orm.dialect = org.hibernate.dialect.OracleDialect
orm.show_sql = true
orm.format_sql = true
orm.hbm2ddl.auto = create

##MVC properties##
mvc.prefix = /WEB-INF/views/
mvc.suffix = .jsp

下面是我的 WebApplicationInitializer 文件

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class AppInit extends AbstractAnnotationConfigDispatcherServletInitializer {

    //provivde root configuration classes to FrontController something like providing web.xml to ServletContainer
    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class[] {AppConfig.class};
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        // TODO Auto-generated method stub
        return null;
    }

    //URL pattern
    @Override
    protected String[] getServletMappings() {
        return new String[] {"/"};
    }

}

在 tomcat 9.0 Web 服务器中运行应用程序时，出现以下异常

WARNING: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sf' defined in AppConfig: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.orm.hibernate5.LocalSessionFactoryBean]: Factory method 'sf' threw exception; nested exception is java.lang.NullPointerException
Feb 15, 2020 7:09:54 PM org.springframework.web.context.ContextLoader initWebApplicationContext
SEVERE: Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sf' defined in AppConfig: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.orm.hibernate5.LocalSessionFactoryBean]: Factory method 'sf' threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:656)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:484)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:860)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:401)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:292)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:103)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4680)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5150)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1377)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1367)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.base/java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:140)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:902)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:841)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1377)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1367)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.base/java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:140)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:902)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:421)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:932)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:633)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:344)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:475)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.orm.hibernate5.LocalSessionFactoryBean]: Factory method 'sf' threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:651)
    ... 45 more
Caused by: java.lang.NullPointerException
    at java.base/java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011)
    at java.base/java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006)
    at java.base/java.util.Properties.put(Properties.java:1331)
    at AppConfig.props(AppConfig.java:57)
    at AppConfig.sf(AppConfig.java:45)
    at AppConfig$$EnhancerBySpringCGLIB$$dbf03bd2.CGLIB$sf$4(<generated>)
    at AppConfig$$EnhancerBySpringCGLIB$$dbf03bd2$$FastClassBySpringCGLIB$$69575c9b.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:363)
    at AppConfig$$EnhancerBySpringCGLIB$$dbf03bd2.sf(<generated>)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
    ... 46 more

Feb 15, 2020 7:09:54 PM org.apache.catalina.core.StandardContext listenerStart
SEVERE: Exception sending context initialized event to listener instance of class [org.springframework.web.context.ContextLoaderListener]
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sf' defined in AppConfig: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.orm.hibernate5.LocalSessionFactoryBean]: Factory method 'sf' threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:656)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:484)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:860)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:401)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:292)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:103)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4680)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5150)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1377)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1367)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.base/java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:140)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:902)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:841)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1377)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1367)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.base/java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:140)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:902)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:421)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:932)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:633)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:344)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:475)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.orm.hibernate5.LocalSessionFactoryBean]: Factory method 'sf' threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:651)
    ... 45 more
Caused by: java.lang.NullPointerException
    at java.base/java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011)
    at java.base/java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006)
    at java.base/java.util.Properties.put(Properties.java:1331)
    at AppConfig.props(AppConfig.java:57)
    at AppConfig.sf(AppConfig.java:45)
    at AppConfig$$EnhancerBySpringCGLIB$$dbf03bd2.CGLIB$sf$4(<generated>)
    at AppConfig$$EnhancerBySpringCGLIB$$dbf03bd2$$FastClassBySpringCGLIB$$69575c9b.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:363)
    at AppConfig$$EnhancerBySpringCGLIB$$dbf03bd2.sf(<generated>)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
    ... 46 more

请指导我如何解决此问题并解释为什么会发生？

Answer 1

您收到空指针异常，因为您尝试将空值放入属性中。检查 props() 方法并查明您是否从环境中获取非空值。

提示:问题出在第 57 行的属性