用java和MySQL实现访客管理系统的黑名单增删改查功能，并且已经包含了异常处理的代码，

以下是一个简单的访客管理系统的黑名单增删改查功能的Java代码，使用MySQL作为数据库：

import java.sql.*;

public class VisitorManagementSystem {
    private static final String DB_URL = "jdbc:mysql://localhost:3306/visitor_management";
    private static final String DB_USER = "root";
    private static final String DB_PASSWORD = "password";

    private Connection conn = null;

    public VisitorManagementSystem() throws SQLException {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
        } catch (ClassNotFoundException e) {
            System.out.println("MySQL JDBC driver not found.");
            e.printStackTrace();
        }
    }

    public void addVisitorToBlacklist(String name) {
        try {
            PreparedStatement stmt = conn.prepareStatement("INSERT INTO blacklist (name) VALUES (?)");
            stmt.setString(1, name);
            stmt.executeUpdate();
            System.out.println(name + " has been added to the blacklist.");
        } catch (SQLException e) {
            System.out.println("Failed to add " + name + " to the blacklist.");
            e.printStackTrace();
        }
    }

    public void removeVisitorFromBlacklist(String name) {
        try {
            PreparedStatement stmt = conn.prepareStatement("DELETE FROM blacklist WHERE name = ?");
            stmt.setString(1, name);
            int rowsUpdated = stmt.executeUpdate();
            if (rowsUpdated > 0) {
                System.out.println(name + " has been removed from the blacklist.");
            } else {
                System.out.println(name + " is not in the blacklist.");
            }
        } catch (SQLException e) {
            System.out.println("Failed to remove " + name + " from the blacklist.");
            e.printStackTrace();
        }
    }

    public void updateVisitorInBlacklist(String oldName, String newName) {
        try {
            PreparedStatement stmt = conn.prepareStatement("UPDATE blacklist SET name = ? WHERE name = ?");
            stmt.setString(1, newName);
            stmt.setString(2, oldName);
            int rowsUpdated = stmt.executeUpdate();
            if (rowsUpdated > 0) {
                System.out.println(oldName + " has been updated to " + newName + " in the blacklist.");
            } else {
                System.out.println(oldName + " is not in the blacklist.");
            }
        } catch (SQLException e) {
            System.out.println("Failed to update " + oldName + " in the blacklist.");
            e.printStackTrace();
        }
    }

    public void searchVisitorInBlacklist(String name) {
        try {
            PreparedStatement stmt = conn.prepareStatement("SELECT name FROM blacklist WHERE name = ?");
            stmt.setString(1, name);
            ResultSet rs = stmt.executeQuery();
            if (rs.next()) {
                System.out.println(name + " is in the blacklist.");
            } else {
                System.out.println(name + " is not in the blacklist.");
            }
        } catch (SQLException e) {
            System.out.println("Failed to search " + name + " in the blacklist.");
            e.printStackTrace();
        }
    }

    public void closeConnection() throws SQLException {
        if (conn != null) {
            conn.close();
        }
    }

    public static void main(String[] args) {
        try {
            VisitorManagementSystem vms = new VisitorManagementSystem();
            vms.addVisitorToBlacklist("John");
            vms.addVisitorToBlacklist("Mary");
            vms.searchVisitorInBlacklist("John");
            vms.searchVisitorInBlacklist("Jane");
            vms.updateVisitorInBlacklist("John", "Johnny");
            vms.searchVisitorInBlacklist("John");
            vms.searchVisitorInBlacklist("Johnny");
            vms.removeVisitorFromBlacklist("Mary");
            vms.removeVisitorFromBlacklist("Jane");
            vms.closeConnection();
        } catch (SQLException e) {
            System.out.println("Failed to connect to the database.");
            e.printStackTrace();
        }
    }
}

上述代码中，我们首先定义了数据库的相关参数，然后在构造函数中使用JDBC驱动程序连接到MySQL数据库。我们实现了四个功能，分别为添加黑名单、删除黑名单、更新黑名单和搜索黑名单。对于每个功能，我们使用PreparedStatement对象执行SQL语句，使用try-catch块进行异常处理。

在main函数中，我们创建了一个VisitorManagementSystem对象，并演示了上述四个功能。最后，我们关闭了数据库连接。