Question

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

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：

这是我的回音类路径 - ＆gt;

C：\ Documents and Settings \ user＆gt; 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

你在哪里声明变量“driverName”？

Answer 2

您初始化但从不使用driver。

您使用driverName但从未对其进行初始化。

解决方案就像将driverName更改为driver一样简单吗？：）

修改：

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块中，或者声明您的方法抛出相同的异常。您选择哪一个导致更清晰的设计，但简单的try/catch可以让编译很快成功。：）

Answer 3

我注意到的第一件事是在这一行：

dbInfo = new DBInfo(new JDBCDriverInfo(driverName, url, username, password), constantsTableName);

在哪里声明了driverName？

尝试将Mysql用于我的Java程序时出错

3 个答案: