java - 在 eclipse 项目中实现嵌入式 Derby 数据库时出现问题？

Question

我正在尝试创建一个表，插入表中并使用 Derby 打印表的内容(如下所示)。

TestProject 类:

package com.user.DerbyTest;

public class TestProject {

    public static void main(String[] args) {
        DBConnection db = new DBConnection();
        db.createTable();
        db.insertIntoTable("todd", 23, 'M');
        db.insertIntoTable("wayne", 54, 'M');
        db.printAll();
    }
}

DBConnection 类:

package com.user.DerbyTest;

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


public class DBConnection {
    private static final String DRIVER = "org.apache.derby.jdbc.*";
    private static final String JDBC_URL = "jdbc:derby:derbytest;create=true";

    Connection conn;

    public DBConnection(){
        try {
            this.conn = DriverManager.getConnection(JDBC_URL);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        if (this.conn != null){
            System.out.println("Connected to database.");
        }
    }

    public void createTable(){
        try {
            conn.createStatement().execute("Create TABLE MyDerbytable(Name varchar(50), Age INT, Gender char(1))");
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }


    public void insertIntoTable(String name, int age, char gender){
        try {
            conn.createStatement().execute("INSERT INTO MyDerbytable Values ("+name+","+age+","+gender+")");
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void printAll(){
        try {
            Statement statement = this.conn.createStatement();
            ResultSet res = statement.executeQuery("Select * FROM MyDerbytable");

            while(res.next()){
                System.out.println(res.getString("Name") + res.getString("Age") + res.getString("Gender"));
            }


        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }   
}

尝试运行此程序时出现大量错误:

有什么想法吗？

编辑:更改为 DROP 错误:

Answer 1

您的表已存在。尝试 DROP TABLE myderby 表；