java – Class.forName(“com.mysql.jdbc.Driver”).newInstance()

我在Netbeans 7.2上遇到这个错误,它说ClassNotFoundexception和InstantationException.我真的被这个问题困住了.请帮助我.

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws servletexception, IOException {
    try {
        String driver = "com.MysqL.jdbc.Driver";
        con = null;
        String username = "";
        String password = "";

        Class.forName("com.MysqL.jdbc.Driver").newInstance();

        con = DriverManager.getConnection("jdbc:MysqL://localhost:3306/dbname", "root", "password");
        Statement st = con.createStatement();
        ResultSet mar = st.executeQuery("SELECT * FROM table");


        Gson gson = new GsonBuilder().create();
        response.setContentType("application/json");  
        response.setCharacterEncoding("utf-8"); 

    } catch (sqlException e) {
                String message = e.getMessage();
    }

解决方法:

这个简单的方法怎么样？！

java.sql.Driver d=new com.MysqL.jdbc.Driver();

我也想知道你为什么用这种方式连接到数据库？！让服务器管理它会更好.

首先配置context.xml(如果你使用的是tomcat),如下所示：

<context>
<Resource name="_ds" auth="Container" type="javax.sql.DataSource"
               maxActive="128" maxIdle="32" username="_admin" password="qwerty" driverClassName="com.MysqL.jdbc.Driver"
               url="jdbc:MysqL://127.0.0.1:3306/dbname"/>
</context>

然后,简单地从servlet / etc中的这个资源获取连接,如下所示：

public void init() {
    try {
        _ds = (DataSource) InitialContext.lookup("java:/comp/env/_ds");
    } catch (Exception ex) {
    }
}

private javax.sql.DataSource _ds;

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws servletexception, IOException
{
    try {
        /*String driver = "com.MysqL.jdbc.Driver";
        con = null;
        String username = "";
        String password = "";

        Class.forName("com.MysqL.jdbc.Driver").newInstance();

        con = DriverManager.getConnection("jdbc:MysqL://localhost:3306/dbname", "root", "password");*/
        Connection con=_ds.getConnection();
        Statement st = con.createStatement();
        ResultSet mar = st.executeQuery("SELECT * FROM table");


        Gson gson = new GsonBuilder().create();
        response.setContentType("application/json");  
        response.setCharacterEncoding("utf-8"); 
        con.close();
    } catch (sqlException e) {
        String message = e.getMessage();
    }

顺便说一句,不要忘记在< CATALINA_BASE> / lib文件夹中编写MysqL JDBC驱动程序jar文件.