Java 无法在 HandlerInterceptorAdapter 中自动装配服务
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StackOverFlow
Cannot Autowire Service in HandlerInterceptorAdapter
提问by dtrunk
I'm getting a NullPointerExceptionwhen trying to @Autowiremy @Service:
我NullPointerException在尝试@Autowire我的时候得到了一个@Service：
public class PagePopulationInterceptor extends HandlerInterceptorAdapter {
private @Autowired MyService service;
public @Override void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView mav) {
service.savePageView(IPUtils.toLong(request.getRemoteAddr()), request.getRequestURI(), request.getHeader("User-Agent"));
mav.addObject("counter", service.getCounter());
}
}
@Configuration
@ComponentScan(basePackages = "com.mycompany", excludeFilters = { @ComponentScan.Filter(Configuration.class) })
@PropertySource("classpath:application.properties")
@EnableTransactionManagement
@EnableWebMvc
public class MyConfig extends WebMvcConfigurerAdapter {
public @Override void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new PagePopulationInterceptor());
}
}
@Service
@Transactional
public class MyService {
private @Autowired PageViewDao pageViewDao;
public class Counter {
private long total;
private long today;
private long yesterday;
private long now;
// Getters and setters
}
public void savePageView(long ip, String visitPage, String userAgent) {
PageView obj = new PageView();
obj.setVisitDate(new Date());
obj.setUserAgent(userAgent);
obj.setPage(visitPage);
obj.setIp(ip);
pageViewDao.saveOrUpdate(obj);
}
public Counter getCounter() {
Counter ret = new Counter();
// populate Counter members
return ret;
}
}
EDIT: Here's the Stacktrace:
编辑：这是堆栈跟踪：
java.lang.NullPointerException
com.mycompany.util.PagePopulationInterceptor.postHandle(PagePopulationInterceptor.java:22)
org.springframework.web.servlet.HandlerExecutionChain.applyPostHandle(HandlerExecutionChain.java:149)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:934)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
采纳答案by Sotirios Delimanolis
That's because Spring isn't managing your PagePopulationInterceptorinstance. You are creating it yourself in the below code
那是因为 Spring 没有管理您的PagePopulationInterceptor实例。您在下面的代码中自己创建它
public @Override void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new PagePopulationInterceptor());
}
change that to
将其更改为
@Bean
public PagePopulationInterceptor pagePopulationInterceptor() {
return new PagePopulationInterceptor();
}
public @Override void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(pagePopulationInterceptor());
}
In this way, Spring will manage the lifecycle of the PagePopulationInterceptorinstance since it's generated from a @Beanmethod. Spring will scan it for @Autowiredtargets and inject them.
这样，Spring 将管理PagePopulationInterceptor实例的生命周期，因为它是从@Bean方法生成的。Spring 将扫描它寻找@Autowired目标并注入它们。
This assumes that PagePopulationInterceptoris in a package to be @ComponentScaned.
这假设PagePopulationInterceptor在要@ComponentScan编辑的包中。
