set the classpath in order to connect between mysql to jdbc

问题

I use the programs: eclipse and mysql.

I have a database in mysql and I want to connect between the eclipse to the mysql.

I have some folders in my project that I created in the eclipse.

I have the main folder: testest.. and I show you what I have in the relevant folders:

testest
..src
....testest
......testestservlet.java
..app engine sdk
..JRE system library
..referenced library
..war
..lib
....mysql-connector-java-5.1.22

I updated my testestservlet.java:

package testest;

import java.io.IOException;
import javax.servlet.http.*;
import java.sql.*;

@SuppressWarnings("serial")
public class TestestServlet extends HttpServlet {
  public void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws IOException {
      resp.setContentType("text/plain");
      resp.getWriter().println("Hey, world");
      resp.getWriter().println("MySQL Connect Example.");
      Connection conn = null;
      String url = "jdbc:mysql://localhost:3306/";
      String dbName = "database_alon";
      String driver = "com.mysql.jdbc.Driver";
      String userName = "root"; 
      String password = "ADMINALON";
      try {
          Class.forName(driver).newInstance();
          conn = DriverManager.getConnection(url+dbName,userName,password);
          resp.getWriter().println("Connected to the database");
          conn.close();
          resp.getWriter().println("Disconnected from database");
      } catch (Exception e) {
          e.printStackTrace(); 
      }
  }
}

now, I run testest by run as->web application.

enter the url: localhost:8888

and only see the 'hello world'.

I read about that and see that I need to write the command:

set CLASSPATH=%CLASSPATH%;JAVA_HOME\lib;

but what are the url-s of my CLASSPATH and JAVA_HOME should be? I have folders of: c:/program_fils/java and: c:/Jconnector (something like that).

the folder of Jconnector contains a file of: mysql-connector-java-5.1.22.jar

I tried to add the JAR into the libraries via the eclipse (right click on testest->properties->Libraries->add external jar->mysql-connector-java-5.1.22-bin.jar:

p.s, my operating system is windows 32bit.

回答1:

There is no need of doing

set CLASSPATH=%CLASSPATH%;JAVA_HOME\lib;

Just add mysql-connector-java-5.1.22-bin.jar: to /WEB-INF/lib directory.

Eclipse is smart enough to recognize .jar files added under /WEB-INF/lib and should include in the CLASSPATH.

Adding a library using "Add External Jar" should also work but its not best practice.

Dropping ".jar" inside /WEB-INF/lib will also work when you externally deploy your web apllication using .war

回答2:

Adding the mysql-connector-java-5.1.22-bin.jar to WE-INF\LIB should resolve this issue. Adding jar file via

properties -> build path -> add external jar

is not a sure shot siolution as various platforms of Eclipse behave differently. However adding the above mentioned jar file should surely make the JDBC program work.

来源：https://stackoverflow.com/questions/13442747/set-the-classpath-in-order-to-connect-between-mysql-to-jdbc

标签

java

mysql

jdbc

classpath