Spring 如何通过ApplicationContext instant直接使用bean
How to use bean directly by ApplicationContext instant in Spring
我正在尝试使用 Spring 中的 ApplicationContext 访问 UserService class。
这是我的控制器 class
package com.dilini.controller;
import com.dilini.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller
public class HelloController {
@Autowired
private ApplicationContext applicationContext;
UserService userService = (UserService) applicationContext.getBean(UserService.class);
@RequestMapping("hi")
@ResponseBody
public String hi() {
return "User count is " + userService.findNumberOfUsers();
}
}
这是我的服务class
package com.dilini.service;
import org.springframework.stereotype.Service;
@Service
public interface UserService {
public int findNumberOfUsers();
}
这是我的服务实现 class。
package com.dilini.service.impl;
import com.dilini.service.UserService;
import org.springframework.stereotype.Service;
@Service("UserService")
public class UserServiceImpl implements UserService {
@Override
public int findNumberOfUsers() {
return 50;
}
}
当我 运行 应用程序时，我得到 Null point exception。
Exception
javax.servlet.ServletException: Servlet.init() for servlet [dispatcher] threw exception
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)
Root Cause
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'helloController' defined in file [C:\Users\dilin\Documents\NetBeansProjects\mvcquick\target\mvcquick-1.0-SNAPSHOT\WEB-INF\classes\com\dilini\controller\HelloController.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.dilini.controller.HelloController]: Constructor threw exception; nested exception is java.lang.NullPointerException
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1101)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
org.springframework.beans.factory.support.AbstractBeanFactory.getObject(AbstractBeanFactory.java:303)
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:663)
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:535)
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:489)
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
javax.servlet.GenericServlet.init(GenericServlet.java:158)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)
Root Cause
org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.dilini.controller.HelloController]: Constructor threw exception; nested exception is java.lang.NullPointerException
org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:163)
org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:89)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1094)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
org.springframework.beans.factory.support.AbstractBeanFactory.getObject(AbstractBeanFactory.java:303)
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:663)
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:535)
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:489)
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
javax.servlet.GenericServlet.init(GenericServlet.java:158)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)
Root Cause
java.lang.NullPointerException
com.dilini.controller.HelloController.<init>(HelloController.java:25)
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
java.lang.reflect.Constructor.newInstance(Constructor.java:422)
org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147)
org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:89)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1094)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
org.springframework.beans.factory.support.AbstractBeanFactory.getObject(AbstractBeanFactory.java:303)
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:663)
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:535)
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:489)
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
javax.servlet.GenericServlet.init(GenericServlet.java:158)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)
你能告诉我为什么会这样吗？
我没有正确使用注释吗？请帮我。
谢谢。
编辑
我正在关注 Spring CookBook 教程。我直接使用 Autowired 访问 Bean 到 UserService 即时。
@Autowired
UserService userService;
@RequestMapping("hi")
@ResponseBody
public String hi() {
return "nb of users: " + userService.findNumberOfUsers();
}
现在我正在尝试这种 ApplicationContext 方法。
您应该通过让 Spring 将 bean 注入您的 class 来做到这一点。例如，使用 @Autowired
@Autowired
UserService userService;
然后 userService 变量将正确引用您的 UserService bean。
编辑：
如果你想专门从 applicationContext 中获取 bean，那么你必须将这段代码 UserService userService = (UserService) applicationContext.getBean(UserService.class); 放在你的 hi() 方法中，以确保 Spring 在你调用之前已经创建并注入了所有必要的依赖项它。
尝试将 UserService userService = (UserService) applicationContext.getBean(UserService.class); 代码移动到 hi() 方法中，例如：
@RequestMapping("hi")
@ResponseBody
public String hi() {
return "User count is " + (UserService) applicationContext.getBean(UserService.class).findNumberOfUsers();
}
如果你想在单例 bean 中注入原型 bean，它会很有用
我正在尝试使用 Spring 中的 ApplicationContext 访问 UserService class。
这是我的控制器 class
package com.dilini.controller;
import com.dilini.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller
public class HelloController {
@Autowired
private ApplicationContext applicationContext;
UserService userService = (UserService) applicationContext.getBean(UserService.class);
@RequestMapping("hi")
@ResponseBody
public String hi() {
return "User count is " + userService.findNumberOfUsers();
}
}
这是我的服务class
package com.dilini.service;
import org.springframework.stereotype.Service;
@Service
public interface UserService {
public int findNumberOfUsers();
}
这是我的服务实现 class。
package com.dilini.service.impl;
import com.dilini.service.UserService;
import org.springframework.stereotype.Service;
@Service("UserService")
public class UserServiceImpl implements UserService {
@Override
public int findNumberOfUsers() {
return 50;
}
}
当我 运行 应用程序时，我得到 Null point exception。
Exception
javax.servlet.ServletException: Servlet.init() for servlet [dispatcher] threw exception
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)
Root Cause
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'helloController' defined in file [C:\Users\dilin\Documents\NetBeansProjects\mvcquick\target\mvcquick-1.0-SNAPSHOT\WEB-INF\classes\com\dilini\controller\HelloController.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.dilini.controller.HelloController]: Constructor threw exception; nested exception is java.lang.NullPointerException
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1101)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
org.springframework.beans.factory.support.AbstractBeanFactory.getObject(AbstractBeanFactory.java:303)
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:663)
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:535)
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:489)
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
javax.servlet.GenericServlet.init(GenericServlet.java:158)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)
Root Cause
org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.dilini.controller.HelloController]: Constructor threw exception; nested exception is java.lang.NullPointerException
org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:163)
org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:89)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1094)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
org.springframework.beans.factory.support.AbstractBeanFactory.getObject(AbstractBeanFactory.java:303)
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:663)
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:535)
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:489)
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
javax.servlet.GenericServlet.init(GenericServlet.java:158)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)
Root Cause
java.lang.NullPointerException
com.dilini.controller.HelloController.<init>(HelloController.java:25)
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
java.lang.reflect.Constructor.newInstance(Constructor.java:422)
org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147)
org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:89)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1094)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
org.springframework.beans.factory.support.AbstractBeanFactory.getObject(AbstractBeanFactory.java:303)
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:663)
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:535)
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:489)
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
javax.servlet.GenericServlet.init(GenericServlet.java:158)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)
你能告诉我为什么会这样吗？
我没有正确使用注释吗？请帮我。
谢谢。
编辑
我正在关注 Spring CookBook 教程。我直接使用 Autowired 访问 Bean 到 UserService 即时。
@Autowired
UserService userService;
@RequestMapping("hi")
@ResponseBody
public String hi() {
return "nb of users: " + userService.findNumberOfUsers();
}
现在我正在尝试这种 ApplicationContext 方法。
您应该通过让 Spring 将 bean 注入您的 class 来做到这一点。例如，使用 @Autowired
@Autowired
UserService userService;
然后 userService 变量将正确引用您的 UserService bean。
编辑：
如果你想专门从 applicationContext 中获取 bean，那么你必须将这段代码 UserService userService = (UserService) applicationContext.getBean(UserService.class); 放在你的 hi() 方法中，以确保 Spring 在你调用之前已经创建并注入了所有必要的依赖项它。
尝试将 UserService userService = (UserService) applicationContext.getBean(UserService.class); 代码移动到 hi() 方法中，例如：
@RequestMapping("hi")
@ResponseBody
public String hi() {
return "User count is " + (UserService) applicationContext.getBean(UserService.class).findNumberOfUsers();
}
如果你想在单例 bean 中注入原型 bean，它会很有用