java - 尝试将 Mysql 用于我的 Java 程序时出错

Question

我在尝试编译以下代码时遇到此错误。我怀疑该代码不支持MySQL。我想使用MySQL并尝试修改它，但无法编译。

QuadrantSystemRDB.java:183: cannot find symbol
symbol  : variable driverName
location:class edu.indiana.iucbrf.examples.quadrantRDBTemplate.QuadrantSystemRD
B
        dbInfo = new DBInfo(new JDBCDriverInfo(driverName, url, username, passwo
rd),constantsTableName);
                                               ^
Note: QuadrantSystemRDB.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error

代码:

    private void setupInfo() {

    Driver driver = new com.mysql.jdbc.Driver();
    String url = "jdbc:mysql://localhost:3306/test";
    String username = "root";
    String password = "123456";

    String problemFeatureSpecTableName = "ProblemFeatureSpec";
    String solutionFeatureSpectTableName = "SolutionFeatureSpec";
    String classTableName = "Class";
    String extraDataTableName = "ExtraData";
    String casebaseTablename = "CaseBase";
    String problemTableName = "Problem";
    String solutionTableName = "Solution";
    String inactiveContextsTableName = "InactiveContext";
    String constantsTableName = "Constants";
    dbInfo = new DBInfo(new JDBCDriverInfo(driverName, url, username, password),constantsTableName);
    problemSpecInfo = new FeatureSpecRDBInfo(problemFeatureSpecTableName, classTableName, extraDataTableName);
    solutionSpecInfo = new FeatureSpecRDBInfo(solutionFeatureSpectTableName, classTableName, extraDataTableName);
    rdbCasebaseInfo = new RDBCaseBaseInfo(casebaseTablename, solutionTableName, problemTableName, inactiveContextsTableName);
}

编辑:

这是我的回显类路径-->

C:\Documents and Settings\user>echo %classpath% .;C:\Program Files\Java\jre6\lib\ext\QTJava.zip;C:\iucbrf\;C:\mysql-connector-ja va-5.1.14-bin.jar;C:\iucbrf.jar

编辑2:

我将 driverName 更改为 driver。 现在错误是...

 QuadrantSystemRDB.java:167: unreported exception java.sql.SQLException; must be
 caught or declared to be thrown
            Driver driver = new com.mysql.jdbc.Driver();
                            ^
 Note: QuadrantSystemRDB.java uses unchecked or unsafe operations.
 Note: Recompile with -Xlint:unchecked for details.
 1 error

编辑3:

try
  {
    Driver driver = new com.mysql.jdbc.Driver();
    String url = "jdbc:mysql://localhost:3306/test";
    String username = "root";
    String password = "123456";

catch (Exception e)
  {
   // message.
  }

Answer 1

您初始化但从未使用驱动程序。

您使用driverName，但从未初始化它。

解决方案是否像将 driverName 更改为 driver 一样简单？ :)

编辑:

QuadrantSystemRDB.java:167: unreported exception java.sql.SQLException; must be
caught or declared to be thrown
    Driver driver = new com.mysql.jdbc.Driver();

我认为com.mysql.jdbc.Driver()可以抛出异常；您需要将其包装在 try/catch block 中，或者声明您的方法抛出相同的异常。您选择哪一个会带来更简洁的设计，但简单的 try/catch 可以让编译非常快速地成功。 :)