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我不知道是否有人能解釋爲什麼在一個DAO下面的代碼在Spring和Hibernate Web應用程序：Hibernate的DAO獲得方法是行不通的，確實否則
@Override
public Book get(Integer bookId) {
logger.info(BookDAOImpl.class.getName() + ".get() method called.");
Session session = sessionFactory.openSession();
try {
System.out.println("Book : " + bookId);
Book book = (Book) session.get(Book.class, bookId);
return book;
}
finally {
session.close();
}
}
將會很好地工作中其父Web應用程序，但是當通過controller和service類通過REST調用：
// Gets a Book via REST.
@RequestMapping(value="/book/{bookId}", method=RequestMethod.GET)
public @ResponseBody Object getBook(@PathVariable("bookId") String bookId) {
logger.info(RestController.class.getName() + ".getBook() method called.");
if (bookIdValid(bookId)) {
Book book = bookService.get(Integer.parseInt(bookId));
System.out.println("ABook " + book.toString());
return book;
}
else {
Messages messages = new Messages();
messages.addMessage(messageSource.getMessage("bookId.required", null, null));
return messages;
}
}
線Book book = (Book) session.get(Book.class, bookId);返回null。
線BookDAOImpl 53是在下面的方法行return bookId == book.getBookId().intValue();：
@Override
public boolean check(Integer bookId) {
logger.info(BookDAOImpl.class.getName() + ".check() method called.");
try {
Book book = this.get(bookId);
return bookId == book.getBookId().intValue();
}
catch(IndexOutOfBoundsException e) {
return false;
}
}
堆棧跟蹤是：
Book : 78
INFO|12 07 2015|22 07 16|http-apr-8080-exec-123|library.controller.PersonController| - library.controller.ExceptionController.exception() method called.
null
library.dao.BookDAOImpl.check(BookDAOImpl.java:53)
library.service.BookServiceImpl.check(BookServiceImpl.java:32)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:483)
org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:201)
com.sun.proxy.$Proxy571.check(Unknown Source)
library.controller.RestController.bookIdValid(RestController.java:127)
library.controller.RestController.getBook(RestController.java:102)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:483)
org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)
org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:690)
org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
javax.servlet.http.HttpServlet.service(HttpServlet.java:618)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:301)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:136)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:74)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:516)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1015)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:652)
org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:277)
org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2451)
org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2440)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
java.lang.Thread.run(Thread.java:744)
library.interceptor.ClientInterceptor.afterCompletion() method completed: GET: /Library/rest/book/78?null at 12 07 2015 @ 22 07 ended with HTTP code: 500.
你確定這本書78是存在的嗎？如果> = Java 8，我會得到'可選'並使用「try-with-resources」來關閉，而不是「finally」，這可能會導致NPE。 –
xenoterracide
我沒有返回null。它在BookDAOImpl.java的第53行拋出一個異常，可能是NullPointerException。這條線是什麼？向我們展示服務和DAO的完整相關代碼。特別是如何聲明和初始化字段。 –
這是一個Java 1.7項目。 get方法的'bookId'參數被填充並且在某些情況下調用'get'的'check'方法被附加到問題中。 –