Доступ к MS Access DB из веб-приложения

Question

Я получаю ошибку ниже при попытке доступа к таблице в MS Access DB.

Я создал БД отдельно.

Ниже приведен код.

public String ValidateLogin(String un, String pw) 
{ 
    try 
    { 

     // Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); 
      String url = "jdbc:ucanaccess://D:/questions1.accdb"; 
      Connection con = DriverManager.getConnection(url, "", ""); 
      Statement s =con.createStatement(); 

      String query="select count(*) from Users where UserName="+un; 
      System.out.println(query); 
      s.execute(query); 

      ResultSet rs= s.getResultSet(); 
      if(rs==null) 
      { 
       result="failure"; 
      } 
      else 
      { 
       String a1=rs.getString(3); 
       if(a1.equals(pw)) 
       { 
        result="success"; 
       } 
       else 
       { 
        result="failure"; 
       } 
      } 
     } 
     catch(Exception e) 
     { 
      e.printStackTrace(); 
     } 
    return result; 
} 

Когда я пытаюсь найти количество записей, он работает нормально. Но когда я пытаюсь получить записи для одного пользователя, это дает мне ошибку.

Скажите, пожалуйста, что нужно сделать.

net.ucanaccess.jdbc.UcanaccessSQLException: UCAExc:::3.0.4 user lacks privilege or object not found: AAA 
    at net.ucanaccess.jdbc.UcanaccessStatement.execute(UcanaccessStatement.java:154) 
    at com.infy.dao.LoginActionDAO.ValidateLogin(LoginActionDAO.java:32) 
    at com.infy.HelloWorldAction.execute(HelloWorldAction.java:33) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:498) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:452) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:291) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:254) 
    at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176) 
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263) 
    at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) 
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:133) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207) 
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207) 
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:142) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:166) 
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:190) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187) 
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52) 
    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:488) 
    at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) 
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859) 
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) 
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) 
    at java.lang.Thread.run(Thread.java:745) 
Caused by: java.sql.SQLSyntaxErrorException: user lacks privilege or object not found: AAA 
    at org.hsqldb.jdbc.Util.sqlException(Unknown Source) 
    at org.hsqldb.jdbc.Util.sqlException(Unknown Source) 
    at org.hsqldb.jdbc.JDBCStatement.fetchResult(Unknown Source) 
    at org.hsqldb.jdbc.JDBCStatement.execute(Unknown Source) 
    at net.ucanaccess.jdbc.Execute.executeWrapped(Execute.java:56) 
    at net.ucanaccess.jdbc.AbstractExecute.executeBase(AbstractExecute.java:152) 
    at net.ucanaccess.jdbc.Execute.execute(Execute.java:46) 
    at net.ucanaccess.jdbc.UcanaccessStatement.execute(UcanaccessStatement.java:152) 
    ... 66 more 
Caused by: org.hsqldb.HsqlException: user lacks privilege or object not found: AAA 
    at org.hsqldb.error.Error.error(Unknown Source) 
    at org.hsqldb.error.Error.error(Unknown Source) 
    at org.hsqldb.ExpressionColumn.checkColumnsResolved(Unknown Source) 
    at org.hsqldb.QueryExpression.resolve(Unknown Source) 
    at org.hsqldb.ParserDQL.compileCursorSpecification(Unknown Source) 
    at org.hsqldb.ParserCommand.compilePart(Unknown Source) 
    at org.hsqldb.ParserCommand.compileStatements(Unknown Source) 
    at org.hsqldb.Session.executeDirectStatement(Unknown Source) 
    at org.hsqldb.Session.execute(Unknown Source) 
    ... 72 more 

Answer 1

Вы получаете ошибку

net.ucanaccess.jdbc.UcanaccessSQLException: UCAExc ::: 3.0.4 пользователь не имеет привилегий или объект не найден: AAA

потому, что ваш код создает SQL-запрос

select count(*) from Users where UserName=AAA 

и AAA является интерпретируется как имя столбца, а не строковое значение.

Правильное решение заключается в использовании PreparedStatement для выполнения параметризованного запроса, который будет выглядеть следующим образом:

String query = "SELECT * FROM Users WHERE UserName=?"; 
PreparedStatement s = con.prepareStatement(query); 
s.setString(1, un); 
ResultSet rs = s.executeQuery(); 
if (rs.next()) { 
    // matching row found, so continue processing 
} else { 
    // no matching row found, so inform user and/or log error 
}