试图从java访问MySQL，但不起作用

Question

我写这个类是为了帮助从我的android项目的MySQL数据库中获取数据，但每次我运行应用程序时，它都会崩溃，有人能告诉我我的代码出了什么问题吗？我对此是新的，所以任何帮助都将非常感谢。

以下是错误消息所说的内容。

04-15 18:46:58.058 158 37-15837/com.example.tomb3.data e/androidruntime：致命异常：main process:com.example.tomb3.data,pid:15837 java.lang.noClassDefFounderRorr：解析失败：ljUnit/runner/version；在com.example.tomb3.data.mysql.getData(Mysql.java:37)在com.example.tomb3.data.mainActivity.oncreate(mainActivity.java:14)在Android.app.activity.performCreate(activity.java:6237)在Android.app.instrumentation.CallActivityonCreate(activity.java:1107)在Android.app.activityThread.performLaunchActivity(activity.java:1107)，在java）在Android.app.activityThread$h.handleMessage(activityThread.java:1344)在Android.os.handler.dispatchMessage(handler.java:102)在Android.os.handler.dispatchMessage(handler.java:148)在Android.os.looper.loop(looper.java:148)在Android.app.activityThread.main(activityThread.java:5417)在）由：java.lang.ClassNotFoundException引起：在路径上没有找到类“junit.runner.version”：dexpathlist[[zip文件“/data/app/com.example.tomb3.data-1/base.apk”],nativelibraryDirectories=[/data/app/com.example.tomb3.data-1/lib/x86,/vendor/lib,/system/lib]]在dalvik.system.basedexClassLoader.findclass（basedexClassLoader.java:56)在java.lang.classLoader.loadClass（classLoader.java:511)在在com.example.tomb3.data.mainactivity.oncreate(mainactivity.java:14) 在Android.app.activity.performCreate(activity.java:6237) 在Android.app.instrumentation.callActivityonCreate(instrumentation.java:1107) 在Android.app.activitythread.performLaunchActivity(activitythread.java:2369) 在Android.app.activitythread.HandleLaunchActivity(activitythread.java:2476) 在Android.app.activitythread.-Wrap11(activitythread.java) 在Android.app.activitythread$h.handleMessage(activitythread.java:1344) 在Android.os.handler.DispatchMessage(Handler.java:102) 在Android.os.looper.loop(looper.java:148) 在Android.app.activitythread.main（activitythread.java:5417) 在java.lang.reflect.Method.invoke（本机方法） 在com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:726) 在com.android.internal.os.zygoteinit.main(zygoteinit.java:616) 禁止：java.lang.ClassNotFoundException:Junit.runner.version在java.lang.bootClassLoader.FindClass（本机方法）在java.lang.bootClassLoader.FindClass（ClassLoader.java:781)在java.lang.bootClassLoader.LoadClass（ClassLoader.java:841)在java.lang.ClassLoader.LoadClass（ClassLoader.java:504)...15多个原因是：没有可用的堆栈跟踪

public class mySql {
    String url;
    String user;
    String password;


    public mySql(String url, String user, String password){
        this.url=url;
        this.user=user;
        this.password=password;
    }
    public String getData(String table){
        Connection con = null;
        Statement st = null;
        ResultSet rs = null;
        String output="";
        try {
            con = DriverManager.getConnection(url, user, password);
            st = con.createStatement();
            rs = st.executeQuery(table);
            if (rs.next()) {
                output += " " + (rs.getString(1));
            }

        } catch (SQLException ex) {
            Logger lgr = Logger.getLogger(Version.class.getName());
            lgr.log(Level.SEVERE, ex.getMessage(), ex);
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (st != null) {
                    st.close();
                }
                if (con != null) {
                    con.close();
                }

            } catch (SQLException ex) {
                Logger lgr = Logger.getLogger(Version.class.getName());
                lgr.log(Level.WARNING, ex.getMessage(), ex);
            }
        }
        return output;
    }
}

Answer 1

仅供参考

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

public class Main {
  public static void main(String[] argv) throws Exception {
    String driver = "com.mysql.jdbc.Driver";

    Class.forName(driver);
    Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/dbname", "user", "password");

    Statement st = con.createStatement();
    int val = st.executeUpdate("INSERT employee VALUES(" + 13 + "," + "'Aman'" + ")");
    System.out.println("1 row affected");

  }
}