Java 无法使用Singleton方法初始化类_Java_Spring_Jdbc

Java 无法使用Singleton方法初始化类

java spring jdbc

Java 无法使用Singleton方法初始化类,java,spring,jdbc,Java,Spring,Jdbc,我创建了一个获取数据库连接实例的类。但是，我得到一个错误，说调用类为null。我将在下面发布我的错误现在我有了这个代码的工作版本和非工作版本。我首先把所有的东西都塞进一个类，让它启动并运行，然后开始清理它，这就是我遇到问题的时候此类“createJobTicket”调用DataBaseConnectionDAO的实例 public class createJobTicket { //private java.sql.Connection conn = null; //pri

我创建了一个获取数据库连接实例的类。但是，我得到一个错误，说调用类为null。我将在下面发布我的错误

现在我有了这个代码的工作版本和非工作版本。我首先把所有的东西都塞进一个类，让它启动并运行，然后开始清理它，这就是我遇到问题的时候

此类“createJobTicket”调用DataBaseConnectionDAO的实例

public class createJobTicket {

    //private java.sql.Connection conn = null;
    //private java.sql.Statement stmt = null;
    private static DataBaseConnectionDAO databaseConnection = DataBaseConnectionDAO.getInstance();

    public static HSSFWorkbook getWorkbook(HSSFWorkbook workbook, Long id, Environment env){

     try{

         java.sql.Connection conn =  databaseConnection.getConnection();
         java.sql.Statement stmt = conn.createStatement();
          String sql;
          sql = "SELECT"
                    +" hillcresttooldie.T_PO.id po_id,"
                    +" hillcresttooldie.T_PO.DUE_DATE due_date,"
                    +" hillcresttooldie.T_CUSTOMER.CUSTOMER_NAME customer_name,"
                    +" hillcresttooldie.T_PART.ID part_id,"
                    +" hillcresttooldie.T_PO_PART.PART_QUANTITY part_quantity,"
                    +" hillcresttooldie.T_PART.PART_NUMBER part_number,"
                    +" hillcresttooldie.T_PART.PART_DESCRIPTION part_description,"
                    +" hillcresttooldie.T_PART.PLASMA_HRS_PER_PART plasma_hrs,"
                    +" hillcresttooldie.T_PART.GRIND_HRS_PER_PART grind_hrs,"
                    +" hillcresttooldie.T_PART.MILL_HRS_PER_PART mill_hrs,"
                    +" hillcresttooldie.T_PART.BRAKEPRESS_HRS_PER_PART brakepress_hrs,"
                    +" hillcresttooldie.T_PART.LASER_HRS_PER_PART laser_hrs,"
                    +" hillcresttooldie.T_MATERIAL.MATERIAL_THICKNESS material_thickness"
                    +" FROM hillcresttooldie.T_PO"
                    +" join hillcresttooldie.T_PO_PART"
                    +" on hillcresttooldie.T_PO_PART.PO_ID = hillcresttooldie.T_PO.ID"
                    +" join hillcresttooldie.T_PART"
                    +" on hillcresttooldie.T_PART.ID = hillcresttooldie.T_PO_PART.PART_ID"
                    +" join hillcresttooldie.T_CUSTOMER"
                    +" on hillcresttooldie.T_PO.CUSTOMER_ID = hillcresttooldie.T_CUSTOMER.ID"
                    +" join hillcresttooldie.T_PART_MATERIAL"
                    +" on hillcresttooldie.T_PART.ID = hillcresttooldie.T_PART_MATERIAL.PARTS_ID"
                    +" join hillcresttooldie.T_MATERIAL"
                    +" on hillcresttooldie.T_PART_MATERIAL.materials_id = hillcresttooldie.T_MATERIAL.id"
                    +" where T_PO.id = '"+id+"'";

         ResultSet rs = stmt.executeQuery(sql);

         int index = 0;

         //STEP 5: Extract data from result set
          while(rs.next()){
             int po_id = rs.getInt("po_id");
             String due_date = rs.getString("due_date");
             String customer_name = rs.getString("customer_name");
             int part_id  = rs.getInt("part_id");
             int part_quantity = rs.getInt("part_quantity");
             String part_number = rs.getString("part_number");
             String part_description = rs.getString("part_description");
             BigDecimal plasma_hrs = rs.getBigDecimal("plasma_hrs");
             BigDecimal grind_hrs = rs.getBigDecimal("grind_hrs");
             BigDecimal mill_hrs = rs.getBigDecimal("mill_hrs");
             BigDecimal brakepress_hrs = rs.getBigDecimal("brakepress_hrs");
             BigDecimal laser_hrs = rs.getBigDecimal("laser_hrs");
             double material_thickness = rs.getDouble("material_thickness");


             //Create the Sheet
             String sheetName = index + "-" + customer_name + "-" + part_number;
             HSSFSheet sheet = workbook.createSheet(sheetName);
             //Apply Template to the sheet
             generateTemplate.applyTemplate(workbook, sheet);


             sheet.getRow(1).createCell(1).setCellValue(po_id);
             sheet.getRow(5).getCell(3).setCellValue(customer_name);
             sheet.getRow(5).createCell(8).setCellValue(due_date);
             sheet.getRow(6).getCell(3).setCellValue(part_number);
             sheet.getRow(6).createCell(8).setCellValue(part_quantity);
             sheet.getRow(7).createCell(4).setCellValue(part_description);
             sheet.getRow(7).createCell(8).setCellValue(material_thickness);


             index++;
          }
          //STEP 6: Clean-up environment
          rs.close();
          stmt.close();
          conn.close();

       }catch(SQLException se){
         se.printStackTrace();
         System.out.println("SQL Exeception thrown");
       }catch(Exception e){
          e.printStackTrace();

       }//end try
    return workbook;

    }

您可以注意到以下内容已被注释掉：

//private java.sql.Connection conn = null;
//private java.sql.Statement stmt = null;

这是因为如果我的IDE说：

 Cannot make a static reference to the non-static field conn
 Cannot make a static reference to the non-static field stmt

我的数据库连接DAO如下所示：

public class DataBaseConnectionDAO {

    @Inject
    private static Environment env;

    private static DataBaseConnectionDAO instance;

    // Step 1: JDBC props
     String DB_URL = env.getProperty("spring.datasource.url");
     String USER = env.getProperty("spring.datasource.username");
     String PASS = env.getProperty("spring.datasource.password");
     java.sql.Connection conn = null;
     java.sql.Statement stmt = null;

    private DataBaseConnectionDAO() { }

    public static DataBaseConnectionDAO getInstance() {

        if (instance == null) {
            synchronized (DataBaseConnectionDAO.class) {
                if (instance == null) {
                    instance = new DataBaseConnectionDAO();
                }
            }
        }
        return instance;
    }

    public java.sql.Connection getConnection() throws ClassNotFoundException,
            SQLException {

        Class.forName("com.mysql.jdbc.Driver");

        if (conn == null) {

            conn = DriverManager.getConnection(DB_URL, USER, PASS);

        }

        return conn;
    }

}


[DEBUG] com.htd.aop.logging.LoggingAspect - Enter: com.htd.web.rest.PoResource.generateJobTicket() with argument[s] = [16, com.codahale.metrics.servlet.AbstractInstrumentedFilter$StatusExposingServletResponse@1424a144]
[ERROR] com.htd.aop.logging.LoggingAspect - Exception in com.htd.web.rest.PoResource.generateJobTicket() with cause = null
java.lang.NoClassDefFoundError: Could not initialize class com.htd.web.rest.util.createJobTicket
    at com.htd.web.rest.PoResource.generateJobTicket(PoResource.java:332) ~[classes/:na]
    at com.htd.web.rest.PoResource$$FastClassBySpringCGLIB$$cfcd338a.invoke(<generated>) ~[spring-core-4.1.6.RELEASE.jar:na]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:717) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at com.htd.aop.logging.LoggingAspect.logAround(LoggingAspect.java:49) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_31]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_31]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_31]
    at java.lang.reflect.Method.invoke(Method.java:483) ~[na:1.8.0_31]
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:68) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:58) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:653) ~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at com.htd.web.rest.PoResource$$EnhancerBySpringCGLIB$$4795e29.generateJobTicket(<generated>) [spring-core-4.1.6.RELEASE.jar:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_31]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_31]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_31]
    at java.lang.reflect.Method.invoke(Method.java:483) ~[na:1.8.0_31]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:618) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842) [spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:725) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at com.codahale.metrics.servlet.AbstractInstrumentedFilter.doFilter(AbstractInstrumentedFilter.java:104) [metrics-servlet-3.1.1.jar:3.1.1]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$ApplicationContextHeaderFilter.doFilterInternal(EndpointWebMvcAutoConfiguration.java:291) [spring-boot-actuator-1.2.3.RELEASE.jar:1.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:316) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:126) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:90) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:122) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:157) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:168) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:48) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:205) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:120) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at com.htd.web.filter.CsrfCookieGeneratorFilter.doFilterInternal(CsrfCookieGeneratorFilter.java:34) [classes/:na]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:96) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:91) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:53) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:213) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:176) [spring-security-web-4.0.0.RELEASE.jar:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:102) [spring-boot-actuator-1.2.3.RELEASE.jar:1.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:516) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1086) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:659) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1558) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1515) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_31]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_31]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.0.20.jar:8.0.20]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_31]

公共类数据库连接DAO{
@注入
私人静态环境；
私有静态数据库连接DAO实例；
//步骤1：JDBC道具
字符串DB_URL=env.getProperty（“spring.datasource.URL”）；
字符串USER=env.getProperty（“spring.datasource.username”）；
字符串PASS=env.getProperty（“spring.datasource.password”）；
java.sql.Connection conn=null；
java.sql.Statement stmt=null；
专用数据库ConnectionDao（）{}
公共静态数据库ConnectionDao getInstance（）{
if（实例==null）{
已同步（DataBaseConnectionDAO.class）{
if（实例==null）{
实例=新数据库ConnectionDao（）；
}
}
}
返回实例；
}
public java.sql.Connection getConnection（）抛出ClassNotFoundException，
SQLException{
Class.forName（“com.mysql.jdbc.Driver”）；
如果（conn==null）{
conn=DriverManager.getConnection（DB_URL，USER，PASS）；
}
返回连接；
}
}
[DEBUG]com.htd.aop.logging.LoggingAspect-输入：com.htd.web.rest.PoResource.generateJobuticket（），参数[s]=[16，com.codahale.metrics.servlet.AbstractInstrumentedFilter$StatusExposingServletResponse@1424a144]
[错误]com.htd.aop.logging.LoggingAspect-com.htd.web.rest.PoResource.generateJobicket（）中的异常，原因为null
java.lang.NoClassDefFoundError:无法初始化类com.htd.web.rest.util.createJobTicket
在com.htd.web.rest.PoResource.generateJobTicket（PoResource.java:332）~[classes/:na]
在com.htd.web.rest.PoResource$$FastClassBySpringCGLIB$$cfcd338a.invoke（）~[spring-core-4.1.6.RELEASE.jar:na]
在org.springframework.cglib.proxy.MethodProxy.invoke（MethodProxy.java:204）~[spring-core-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint（CglibAopProxy.java:717）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.framework.ReflectiveMethodInvocation.procedue（ReflectiveMethodInvocation.java:157）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.procedue（MethodInvocationProceedingJoinPoint.java:85）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在com.htd.aop.logging.LoggingAspect.logAround（LoggingAspect.java:49）~[classes/:na]
在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）~[na:1.8.0\u 31]
在sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62）~[na:1.8.0\u 31]
在sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:43）~[na:1.8.031]
在java.lang.reflect.Method.invoke（Method.java:483）~[na:1.8.0\u 31]
在org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs（AbstractAspectJAdvice.java:621）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod（AbstractAspectJAdvice.java:610）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.aspectj.AspectJAroundAdvice.invoke（AspectJAroundAdvice.java:68）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.framework.ReflectiveMethodInvocation.procedue（ReflectiveMethodInvocation.java:179）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.aspectj.aspectjafthrowingadvice.invoke（aspectjafthrowingadvice.java:58）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.framework.ReflectiveMethodInvocation.procedue（ReflectiveMethodInvocation.java:179）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke（ExposeInvocationInterceptor.java:92）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.framework.ReflectiveMethodInvocation.procedue（ReflectiveMethodInvocation.java:179）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept（CglibAopProxy.java:653）~[spring-aop-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在com.htd.web.rest.PoResource$$EnhancerBySpringCGLIB$$4795e29.generateJobTicket（）[spring-core-4.1.6.RELEASE.jar:na]
在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）~[na:1.8.0\u 31]
在sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62）~[na:1.8.0\u 31]
在sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:43）~[na:1.8.031]
在java.lang.reflect.Method.invoke（Method.java:483）~[na:1.8.0\u 31]
在org.springframework.web.method.support.InvocableHandlerMethod.doInvoke（InvocableHandlerMethod.java:221）[spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest（InvocableHandlerMethod.java:137）[spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]
在org.springframework.web.servlet.mvc.method.annotation.ServletinInvocableHandlerMethod.invokeAndHandle（ServletinInvocableHandlerMethod.java:110）[spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]
位于org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod（RequestMapp
[DEBUG] com.htd.aop.logging.LoggingAspect - Enter: com.htd.web.rest.PoResource.generateJobTicket() with argument[s] = [16, com.codahale.metrics.servlet.AbstractInstrumentedFilter$StatusExposingServletResponse@613cf2e]
[ERROR] com.htd.aop.logging.LoggingAspect - Exception in com.htd.web.rest.PoResource.generateJobTicket() with cause = null
java.lang.NoClassDefFoundError: Could not initialize class com.htd.web.rest.util.createJobTicket
    at com.htd.web.rest.PoResource.generateJobTicket(PoResource.java:332) ~[classes/:na]
    at com.htd.web.rest.PoResource$$FastClassBySpringCGLIB$$cfcd338a.invoke(<generated>) ~[spring-core-4.1.6.RELEASE.jar:na]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.1.6.RELEASE.jar:4.1.6.RELEASE]

    private static DataBaseConnectionDAO databaseConnection = DataBaseConnectionDAO.getInstance();

    private static DataBaseConnectionDAO databaseConnection;

    private static java.sql.Connection getDatabaseConnection() {
        if (databaseConnection == null) {
            databaseConnection = DataBaseConnectionDAO.getInstance();
        }
        return databaseConnection.getConnection();
    }

    public static HSSFWorkbook getWorkbook(HSSFWorkbook workbook, Long id, Environment env){

     try{

         java.sql.Connection conn = getDatabaseConnection();
         // ...

@Inject
private static Environment env;