SQLException：找不到合适的驱动程序

Question

这个问题已经在这里有了答案 ：

臭名昭著的java.sql.SQLException：未找到合适的驱动程序 （13个答案）

4年前关闭。

我有一个Java类，该类通过在Tomcat上运行的JSP中使用的JDBC通过JDBC访问MySQL数据库，并且遇到“未找到驱动程序异常”的问题。

我有一个方法：

private static Statement makeStatement() {
   try{
    com.mysql.jdbc.Driver d = null;
    try{d = new com.mysql.jdbc.Driver();}catch(Exception e){
      System.out.println("ERROR BY NEW DRIVER " + e.toString() + 
      "\n");e.printStackTrace();}
    Connection con = DriverManager.getConnection(url, user, password);
    return con.createStatement();
   }catch(java.sql.SQLException ex){
      System.out.println("ERROR IN makeStatement " + "\nERROR - " +
      ex.toString() +  "\n ERROR CODE:\n " + ex.getErrorCode() + 
      "\nSQLSTATE:\n " + ex.getSQLStat        e());ex.printStackTrace();}
    return null;
 }

这会在“ Connection con = DriverManager.getConnection(url, user, password);这是我从catalina.out的打印输出”上引发错误：

  Received Parameters

ERROR IN makeStatement 
ERROR - java.sql.SQLException: No suitable driver found for 
 ERROR CODE:
 0
SQLSTATE:
 08001
java.sql.SQLException: No suitable driver found for 
        at java.sql.DriverManager.getConnection(DriverManager.java:602)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at message.Message.makeStatement(Message.java:72)
        at message.Message.query(Message.java:79)
        at message.Message.getName(Message.java:225)
        at org.apache.jsp.message_jsp._jspService(message_jsp.java:288)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:548)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
        at java.lang.Thread.run(Thread.java:619)
ERROR IN QUERY java.lang.NullPointerException
ERROR in getName java.lang.NullPointerException
-----------------------------------

  Received Parameters

        newMessage      =  
        newpassword     = 
        verifypassword  = 
        sendinfo        = 
        username        = Eli
        newusername     = 
        login   = login
        password        = tree
ERROR IN makeStatement 
ERROR - java.sql.SQLException: No suitable driver found for 
 ERROR CODE:
 0
SQLSTATE:
 08001
java.sql.SQLException: No suitable driver found for 
        at java.sql.DriverManager.getConnection(DriverManager.java:602)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at message.Message.makeStatement(Message.java:72)
        at message.Message.query(Message.java:79)
        at message.Message.validUser(Message.java:195)
        at org.apache.jsp.message_jsp._jspService(message_jsp.java:123)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:548)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
        at java.lang.Thread.run(Thread.java:619)
ERROR IN QUERY java.lang.NullPointerException
ERROR in validUser java.lang.NullPointerException
ERROR IN makeStatement 
ERROR - java.sql.SQLException: No suitable driver found for 
 ERROR CODE:
 0
SQLSTATE:
 08001
java.sql.SQLException: No suitable driver found for 
        at java.sql.DriverManager.getConnection(DriverManager.java:602)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at message.Message.makeStatement(Message.java:72)
        at message.Message.query(Message.java:79)
        at message.Message.getName(Message.java:225)
        at org.apache.jsp.message_jsp._jspService(message_jsp.java:288)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:548)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
        at java.lang.Thread.run(Thread.java:619)
ERROR IN QUERY java.lang.NullPointerException
ERROR in getName java.lang.NullPointerException

唯一重要的错误是一个，makeStatement()因为失败会导致所有其他错误。我已四重检查我的WEB-INF /
lib目录中是否具有正确的jar文件，并且重新启动Tomcat的次数比我想要的要多。我有一个makeStatement()在不同的.java文件中使用的单独的webapp，该webapp运行良好。更奇怪的是，我在.java中有这个：

static {
  System.err.println("\n\nTEST MYSQL ACCESS: dump all relevant tables:");
  dump();
  System.err.println("END OF MYSQL ACCESS ACCESS.");
}

 public static void dump() {
   try {
     readUsers();
     for (UserRecord u: users)
     System.err.println(u.username+" "+u.password);
   } catch (Exception e) {System.err.println(e);}
 }

使用readUsers()读取数据库中所有用户的位置makeStatement()。这实际上可以正常工作，并且将打印数据库中的所有用户（出于明显的原因未在此处显示:)），然后发生驱动程序未找到错误。

Answer 1

java.sql.SQLException：找不到合适的驱动程序

此异常可能有2个原因：

1. 完全不加载JDBC驱动程序。
2. URL与任何已加载的JDBC驱动程序都不匹配。

由于驱动程序似乎已加载（尽管以错误的方式），因此该URL显然是错误的。确保url变量的值与以下格式匹配

jdbc:mysql://localhost:3306/dbname

也可以看看：

• 将Java连接到MySQL数据库

与 具体问题 无关 ：Java代码不属于JSP文件。也要努力。您的异常处理也很糟糕，您应该 抛出
异常（以使其阻止执行代码的剩余部分），而不是打印消息/跟踪，然后继续执行代码。