Question

我有一个Maven项目正在运行，当我尝试运行GET调用时，它会向控制台输出一个ClassNotFound异常，然后在页面上给我一个null结果。我有一个动态的Web项目，我从中复制/粘贴代码，它可以正常工作。我不知道如何调试它，因为它看起来应该可以工作。

这是错误：

Error: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver0:0:0:0:0:0:0:1 - - [18/Jul/2013:21:35:19 +0000] "GET /parties HTTP/1.1" 200 87 163 163
0:0:0:0:0:0:0:1 - - [18/Jul/2013:21:35:19 +0000] "GET /favicon.ico HTTP/1.1" 404 1329 9 9

以下是代码发生的地方：

    package core;

import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Connection;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.util.HashMap;

public class DBConnection {

    private Connection con;
    private static Statement statement;
    private static ResultSet resultSet;
    public  static DBConnection connection;
    private static ResultSetMetaData meta;
    private static HashMap<String,Party> map;

    public Party party;

    private DBConnection()
    {
        try 
        {
            map = new HashMap<String,Party>();
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection(
                    "jdbc:mysql://atom3.cisco.com:3306/asdf", "asdf",
                    "asdf");
            statement = con.createStatement();
            readData();
        }
        catch (Exception e)
        {
            System.out.print("Error: "+e);
        }
    }
    public void readData()
    {
        try
        {
            map.clear();
            String query = "(SELECT * FROM PureServlet)";
            resultSet = statement.executeQuery(query);
            meta = resultSet.getMetaData();
            String columnName, value, partyName;
            while(resultSet.next())
            {
                partyName = resultSet.getString("PARTY_NAME");
                map.put(partyName, new Party()); //this is the map that keeps track of all parties
                party = map.get(partyName);
                for(int j=1;j<=meta.getColumnCount();j++) //necessary to start at j=1 because of MySQL index starting at 1
                {
                    columnName = meta.getColumnLabel(j);
                    value = resultSet.getString(columnName);
                    party.getPartyInfo().put(columnName, value); //this is the hashmap within the party that keeps 
                    //track of the individual values. The column Name = label, value is the value
                }
            }
        }
        catch (Exception e)
        {
            System.out.println(e);
        }
    }
    public static HashMap<String,Party> getPartyCollection()
    {
        if(connection == null)
        {
            connection = new DBConnection();
        }
        return map;
    }
}

Answer 1

需要添加依赖项。我发誓我以前加了它，一定是不小心删掉了它。

<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>

Answer 2

lib目录中缺少JAR文件（ojdbc6.jar）下载并将其放在lib目录中，然后重试。

为什么Java给我一个ClassNotFoundException？

2 个答案: