Question

I was wondering what’s the error of this code, I get everything right, but why won’t it work? here’s the code, I got my driver name, and database url right, but why is it not working??

package test;

import java.util.List;

import org.springframework.jdbc.datasource.DriverManagerDataSource;

import dao.DerbyDao;
import domainmodel.Person;

public final class Main {
    private Main() {
    };

    public static void main(String[] args) {
        DerbyDao dao = new DerbyDao();
        // Initialize the datasource, could /should be done of Spring
        // configuration
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/persons");
        dataSource.setUsername("root");
        dataSource.setPassword("123192");
        // Inject the datasource into the dao
        dao.setDataSource(dataSource);

        dao.create("Lars", "Vogel");
        dao.create("Jim", "Knopf");
        dao.create("Lars", "Man");
        dao.create("Spider", "Man");
        System.out.println("Now select and list all persons");
        List<Person> list = dao.selectAll();
        for (Person myPerson : list) {
            System.out.print(myPerson.getFirstName() + " ");
            System.out.println(myPerson.getLastName());
        }
        System.out
                .println("Now select and list all persons with have the firstname Lars and lastname Vogel");
        list = dao.select("Lars", "Vogel");
        for (Person myPerson : list) {
            System.out.print(myPerson.getFirstName() + " ");
            System.out.println(myPerson.getLastName());
        }

        // Clean-up
        dao.deleteAll();
    }
}

and this is the error

log4j:WARN No appenders could be found for logger (org.springframework.jdbc.datasource.DriverManagerDataSource).
log4j:WARN Please initialize the log4j system properly.
Exception in thread "main" org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown database 'person'
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:82)
    at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:577)
    at org.springframework.jdbc.core.JdbcTemplate.update(JdbcTemplate.java:792)
    at org.springframework.jdbc.core.JdbcTemplate.update(JdbcTemplate.java:850)
    at org.springframework.jdbc.core.JdbcTemplate.update(JdbcTemplate.java:858)
    at dao.DerbyDao.create(DerbyDao.java:21)
    at test.Main.main(Main.java:26)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown database 'person'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.Util.getInstance(Util.java:386)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1052)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3609)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3541)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:943)
    at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:4113)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1308)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2336)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2369)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at org.springframework.jdbc.datasource.DriverManagerDataSource.getConnectionFromDriverManager(DriverManagerDataSource.java:174)
    at org.springframework.jdbc.datasource.DriverManagerDataSource.getConnectionFromDriver(DriverManagerDataSource.java:165)
    at org.springframework.jdbc.datasource.AbstractDriverBasedDataSource.getConnectionFromDriver(AbstractDriverBasedDataSource.java:149)
    at org.springframework.jdbc.datasource.AbstractDriverBasedDataSource.getConnection(AbstractDriverBasedDataSource.java:119)
    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:113)
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:79)
    ... 6 more

I got my driver right but why is it not working?

EDIT
Person Class

package domainmodel;

public class Person {

    private String firstName;
    private String lastName;

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
}

Here’s the Dao class

package dao;

import java.util.List;

import javax.sql.DataSource;

import org.springframework.jdbc.core.JdbcTemplate;

import dao.mapper.PersonRowMapper;
import domainmodel.Person;

public class DerbyDao implements IDao {
    private DataSource dataSource;

    public void setDataSource(DataSource ds) {
        dataSource = ds;
    }

    public void create(String firstName, String lastName) {
        JdbcTemplate insert = new JdbcTemplate(dataSource);
        insert.update("INSERT INTO PERSON (FIRSTNAME, LASTNAME) VALUES(?,?)",
                new Object[] { firstName, lastName });
    }

    public List<Person> select(String firstname, String lastname) {
        JdbcTemplate select = new JdbcTemplate(dataSource);
        return select
                .query(
                        "select  FIRSTNAME, LASTNAME from PERSON where FIRSTNAME = ? AND LASTNAME= ?",
                        new Object[] { firstname, lastname },
                        new PersonRowMapper());
    }

    public List<Person> selectAll() {
        JdbcTemplate select = new JdbcTemplate(dataSource);
        return select.query("select FIRSTNAME, LASTNAME from PERSON",
                new PersonRowMapper());
    }

    public void deleteAll() {
        JdbcTemplate delete = new JdbcTemplate(dataSource);
        delete.update("DELETE from PERSON");
    }

    public void delete(String firstName, String lastName) {
        JdbcTemplate delete = new JdbcTemplate(dataSource);
        delete.update("DELETE from PERSON where FIRSTNAME= ? AND LASTNAME = ?",
                new Object[] { firstName, lastName });
    }

}

I just got this online, but I tried to convert it for a MySql database, not a Derby database

Answer 1

First check that you are correctly connecting to your database. Create a class for it. Then check your table named “person” exists?

import java.sql.*;

public class MysqlConnect{
  public static void main(String[] args) {
  System.out.println("MySQL Connect Example.");
  Connection conn = null;
  String url = "jdbc:mysql://localhost:3306/";
  String dbName = "persons";
  String driver = "com.mysql.jdbc.Driver";
  String userName = "root"; 
  String password = "123192";
  try {
  Class.forName(driver).newInstance();
  conn = DriverManager.getConnection(url+dbName,userName,password);
  System.out.println("Connected to the database");
  conn.close();
  System.out.println("Disconnected from database");
  } catch (Exception e) {
  e.printStackTrace();
  }
  }
}