java - 尝试记录 sql 请求时 P6Spy 出现 ClassNotFoundException

Question

我遇到了这个异常:

java.lang.ClassNotFoundException: com.p6spy.engine.spy.P6SpyDriver  

尝试通过 P6Spy 代理驱动程序连接到我的数据库时。这个异常指向这行代码:

Class.forName("com.p6spy.engine.spy.P6SpyDriver");  

我将P6Spy.jar和spy.properties添加到构建路径中，这是spy.properties配置文件:

 #################################################################
# P6Spy Options File                                            #
# See documentation for detailed instructions                   #
#################################################################

#################################################################
# MODULES                                                       #
#                                                               #
# Modules provide the P6Spy functionality.  If a module, such   #
# as module_log is commented out, that functionality will not   #
# be available.  If it is not commented out (if it is active),  #
# the functionality will be active.                             #
#                                                               #
# Values set in Modules cannot be reloaded using the            #
# reloadproperties variable.  Once they are loaded, they remain #
# in memory until the application is restarted.                 #
#                                                               #
#################################################################

#module.log=com.p6spy.engine.logging.P6LogFactory
#module.outage=com.p6spy.engine.outage.P6OutageFactory

#################################################################
# REALDRIVER(s)                                                 #
#                                                               #
# In your application server configuration file you replace the #
# "real driver" name with com.p6spy.engine.P6SpyDriver. This is #
# where you put the name of your real driver P6Spy can find and #
# register your real driver to do the database work.            #
#                                                               #
# If your application uses several drivers specify them in      #
# realdriver2, realdriver3.  See the documentation for more     #
# details.                                                      #
#                                                               #
# Values set in REALDRIVER(s) cannot be reloaded using the      #
# reloadproperties variable.  Once they are loaded, they remain #
# in memory until the application is restarted.                 #
#                                                               #
#################################################################

# oracle driver
realdriver=oracle.jdbc.driver.OracleDriver

# mysql Connector/J driver
# realdriver=com.mysql.jdbc.Driver

# informix driver
# realdriver=com.informix.jdbc.IfxDriver

# ibm db2 driver
# realdriver=COM.ibm.db2.jdbc.net.DB2Driver

# the mysql open source driver
#realdriver=org.gjt.mm.mysql.Driver

#specifies another driver to use
#realdriver2=
#specifies a third driver to use
#realdriver3=


#the DriverManager class sequentially tries every driver that is
#registered to find the right driver.  In some instances, it's possible to
#load up the realdriver before the p6spy driver, in which case your connections
#will not get wrapped as the realdriver will "steal" the connection before
#p6spy sees it.  Set the following property to "true" to cause p6spy to
#explicitily deregister the realdrivers
deregisterdrivers=false

################################################################
# P6LOG SPECIFIC PROPERTIES                                    #
################################################################
# no properties currently available

################################################################
# EXECUTION THRESHOLD PROPERTIES                               #
################################################################
# This feature applies to the standard logging of P6Spy.       # 
# While the standard logging logs out every statement          #
# regardless of its execution time, this feature puts a time   # 
# condition on that logging.  Only statements that have taken  # 
# longer than the time specified (in milliseconds) will be     #
# logged.  This way it is possible to see only statements that #
# have exceeded some high water mark.                          #
# This time is reloadable.                                     #
#
# executionthreshold=integer time (milliseconds)
#
#executionthreshold=

################################################################
# P6OUTAGE SPECIFIC PROPERTIES                                 #
################################################################
# Outage Detection
#
# This feature detects long-running statements that may be indicative of
# a database outage problem. If this feature is turned on, it will log any
# statement that surpasses the configurable time boundary during its execution.
# When this feature is enabled, no other statements are logged except the long
# running statements. The interval property is the boundary time set in seconds.
# For example, if this is set to 2, then any statement requiring at least 2 
# seconds will be logged. Note that the same statement will continue to be logged
# for as long as it executes. So if the interval is set to 2, and the query takes
# 11 seconds, it will be logged 5 times (at the 2, 4, 6, 8, 10 second intervals).
#
# outagedetection=true|false
# outagedetectioninterval=integer time (seconds)
#
outagedetection=false
#outagedetectioninterval=

################################################################
# COMMON PROPERTIES                                            #
################################################################

# filter what is logged
filter=false

# comma separated list of tables to include when filtering
include     = 
# comma separated list of tables to exclude when filtering
exclude     =

# sql expression to evaluate if using regex filtering
#sqlexpression = 


# turn on tracing
#autoflush   = true

# sets the date format using Java's SimpleDateFormat routine
dateformat=yyyy-MM-dd

#list of categories to explicitly include 
#includecategories=

#list of categories to exclude: error, info, batch, debug, statement,
#commit, rollback and result are valid values
excludecategories=


#allows you to use a regex engine or your own matching engine to determine 
#which statements to log
#
#stringmatcher=com.p6spy.engine.common.GnuRegexMatcher
#stringmatcher=com.p6spy.engine.common.JakartaRegexMatcher
#stringmatcher=

# prints a stack trace for every statement logged
stacktrace=false
# if stacktrace=true, specifies the stack trace to print
#stacktraceclass=

# determines if property file should be reloaded
#reloadproperties=false
# determines how often should be reloaded in seconds
#reloadpropertiesinterval=60

#if=true then url must be prefixed with p6spy:
useprefix=true

#specifies the appender to use for logging
#appender=com.p6spy.engine.logging.appender.Log4jLogger
#appender=com.p6spy.engine.logging.appender.StdoutLogger
appender=com.p6spy.engine.logging.appender.FileLogger

# name of logfile to use, note Windows users should make sure to use forward slashes in their pathname (e:/test/spy.log) (used for file logger only)
logfile     = D:/spy.log

# append to  the p6spy log file.  if this is set to false the
# log file is truncated every time.  (file logger only)
append=true

#The following are for log4j logging only
#log4j.appender.STDOUT=org.apache.log4j.ConsoleAppender
#log4j.appender.STDOUT.layout=org.apache.log4j.PatternLayout
#log4j.appender.STDOUT.layout.ConversionPattern=p6spy - %m%n

#log4j.appender.CHAINSAW_CLIENT=org.apache.log4j.net.SocketAppender
#log4j.appender.CHAINSAW_CLIENT.RemoteHost=localhost
#log4j.appender.CHAINSAW_CLIENT.Port=4445
#log4j.appender.CHAINSAW_CLIENT.LocationInfo=true

#log4j.logger.p6spy=INFO,STDOUT


#################################################################
# DataSource replacement                                        #
#                                                               #
# Replace the real DataSource class in your application server  #
# configuration with the name com.p6spy.engine.spy.P6DataSource,#
# then add the JNDI name and class name of the real         #
# DataSource here                               #
#                                                               #
# Values set in this item cannot be reloaded using the          #
# reloadproperties variable.  Once it is loaded, it remains     #
# in memory until the application is restarted.                 #
#                                                               #
#################################################################
#realdatasource=/RealMySqlDS
#realdatasourceclass=com.mysql.jdbc.jdbc2.optional.MysqlDataSource

#################################################################
# DataSource properties                                         #
#                                                               #
# If you are using the DataSource support to intercept calls    # 
# to a DataSource that requires properties for proper setup,    #
# define those properties here. Use name value pairs, separate  #
# the name and value with a semicolon, and separate the         #
# pairs with commas.                                            #
#                                           #
# The example shown here is for mysql                           #
#                                                               #
#################################################################
#realdatasourceproperties=port;3306,serverName;ibmhost,databaseName;mydb


#################################################################
# JNDI DataSource lookup                                        #
#                                                               #
# If you are using the DataSource support outside of an app     #
# server, you will probably need to define the JNDI Context     #
# environment.                                                  #
#                                                               #
# If the P6Spy code will be executing inside an app server then #
# do not use these properties, and the DataSource lookup will   #
# use the naming context defined by the app server.             #
#                                                               #
# The two standard elements of the naming environment are   #
# jndicontextfactory and jndicontextproviderurl. If you need    #
# additional elements, use the jndicontextcustom property.      #
# You can define multiple properties in jndicontextcustom,      #
# in name value pairs. Separate the name and value with a       #
# semicolon, and separate the pairs with commas.                #
#                                                               #
# The example shown here is for a standalone program running on #
# a machine that is also running JBoss, so the JDNI context     #
# is configured for JBoss (3.0.4).                              #
#                                                               #
#################################################################
#jndicontextfactory=org.jnp.interfaces.NamingContextFactory
#jndicontextproviderurl=localhost:1099
#jndicontextcustom=java.naming.factory.url.pkgs;org.jboss.nameing:org.jnp.interfaces

#jndicontextfactory=com.ibm.websphere.naming.WsnInitialContextFactory
#jndicontextproviderurl=iiop://localhost:900

append=true    

这是我的连接类:

public class ConnexionBD {
        private static final ConnexionBD INSTANCE= new ConnexionBD();
        private String host;
        private String database;
        private int port;
        private String login;
        private char[] password;
        private String privileges;
        private Connection connection;
        public static final String DATABASE_JDBC_DRIVER = "com.p6spy.engine.spy.P6SpyDriver"; 

    private ConnexionBD() {}

    public static ConnexionBD getInstance() {
        return INSTANCE;
    }


    //getters and setters...

    public Connection getConnection() throws ClassNotFoundException, SQLException {
        String DATABASE_URL=null;

        DATABASE_URL = "p6spy:jdbc:oracle:thin:@"+getHost()+":"+getPort()+":"+getDatabase();

        if (connection!=null) 
        { 
            return connection ; 
        } 
        else{
            Class.forName(DATABASE_JDBC_DRIVER);  

            connection = DriverManager.getConnection(DATABASE_URL,getLogin(),new String(getPassword())) ; 

            return connection ; 
        }
    }
    public void setConnection(Connection connection) {
        this.connection = connection;
    }


}

有人可以告诉我这里出了什么问题吗？非常感谢任何帮助!

Answer 1

看起来 P6SpyDriver 在运行时不在您的类路径中。语句 Class.forName(DATABASE_JDBC_DRIVER); 尝试使用与加载 ConnexionBD 相同的类加载器来加载 P6SpyDriver。无论出于何种原因，该类加载器无权访问该类。

我建议记录向类加载器及其父级注册的 URL。这可能会让您了解为什么会发生这种情况。请参阅下面的代码，了解如何记录类路径位置的示例。只需将方法添加到您的 ConnexionBD 类中，并在 Class.forName(DATABASE_JDBC_DRIVER); 上方的行添加 logClassPath(this); 即可。

  private void logClassPath(final Class clazz) {
    StringWriter sw = new StringWriter();
    PrintWriter pw = new PrintWriter(sw);
    ClassLoader cl = clazz.getClassLoader();
    pw.println("Processing classloader which loaded " + clazz.getName() +" classloader: "+cl.getClass().getName());
    if (cl instanceof URLClassLoader) {
      logUrls(pw, (URLClassLoader) cl);
    } else {
      pw.println("Unsupported classloader - " + cl.getClass().getName());
    }
    while (cl.getParent() != null) {
      cl = cl.getParent();
      pw.println("\n\nProcessing parent classloader" +" classloader: "+cl.getClass().getName());
      if (cl instanceof URLClassLoader) {
        logUrls(pw, (URLClassLoader) cl);
      } else {
        pw.println("Unsupported classloader - " + cl.getClass().getName());
      }
    }
    pw.flush();
    System.out.print(sw.toString());

  }

  private void logUrls(final PrintWriter pw, final URLClassLoader cl) {
    if( cl.getURLs().length == 0 ) {
      pw.println("No URLs registered for this classloader");
    }
    for (URL url : cl.getURLs()) {
      pw.println(url.toString());
    }
  }

我提供的代码仅适用于作为 URLClassloader 实例的类加载器。它还假设您也有分层类加载器。对于普通的 java 应用程序或在轻量级容器中运行的 Web 应用程序来说，这应该没问题。

如果您在基于 OSGI 的容器中运行，那么您将需要使用容器提供的任何工具来排除类加载故障。