我开发了一个servlet，它通过JNDI数据源调用MariaDB数据库。当我在eclipse中运行的tomcat服务器上运行eclipse中的web项目时，这很好用。
但是，当我在eclipse之外的tomcat服务器上部署项目时，使用WAR文件，同一个servlet不起作用。出于测试目的，该项目还包含另一个servlet，它直接连接（即不使用JDNI数据源）到同一个mariaDB，即使部署到eclipse之外的tomcat服务器也可以正常工作。关于可能出现的问题，我的想法已经不多了，如果有人可以解释一下，我会非常感激。
配置信息：
在日食之外，司机在两个地方：
我已将以下资源引用添加到应用程序web.xml文件中：
<resource-ref>
<description>DB Connection</description>
<res-ref-name>jdbc/MYDB</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
我已将以下资源添加到/tomcat-folder/contf/context.xml：
<Resource name="jdbc/MYDB” auth="Container" type="javax.sql.DataSource"
maxTotal="100" maxIdle="30" maxWaitMillis="10000"
username="root" password="" driverClassName="org.mariadb.jdbc.Driver"
url="jdbc:mariadb//localhost:3306/MYDB”/>
我得到的错误是：
java.sql.SQLException: Cannot create JDBC driver of class 'org.mariadb.jdbc.Driver' for connect URL 'jdbc:mariadb//localhost:3306/MYDB'
at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createConnectionFactory(BasicDataSource.java:2167)
at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createDataSource(BasicDataSource.java:2037)
at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.getConnection(BasicDataSource.java:1543)
at DBConfigTest.getConnection(DBConfigTest.java:123)
at DBConfigTest.doGet(DBConfigTest.java:59)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:789)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1437)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.sql.SQLException: No suitable driver
at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createConnectionFactory(BasicDataSource.java:2158)
... 28 more
java.lang.NullPointerException
at DBConfigTest.doGet(DBConfigTest.java:61)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:789)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1437)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
servlet代码如下：
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.naming.NamingException;
import javax.sql.DataSource;
public class DBConfigTest extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// JDBC driver name and database URL
// static final String JDBC_DRIVER = "org.mariadb.jdbc.Driver";
// static final String DB_URL="jdbc:mariadb://localhost/MYDB"+"?user=root&password=";
// Database credentials
// static final String USER = "root";
// static final String PASS = "";
// Set response content type
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Database Result";
String docType =
"<!doctype html public \"-//w3c//dtd html 4.0 " + "transitional//en\">\n";
out.println(docType +
"<html>\n" +
"<head><title>" + title + "</title></head>\n" +
"<body bgcolor = \"#f0f0f0\">\n" +
"<h1 align = \"center\">" + title + "</h1>\n");
// Execute SQL query
//Statement stmt=null;
//Connection conn=null;
Connection connection=null;
PreparedStatement statement=null;
try {
// Register JDBC driver
//Class.forName("org.mariadb.jdbc.Driver");
// Open a connection
//conn = DriverManager.getConnection("jdbc:mariadb://localhost/MYDB"+"?user=root&password=");
connection = getConnection();
String sql = "SELECT * FROM ingredient";
statement = connection.prepareStatement(sql);
ResultSet rs = statement.executeQuery();
// Execute SQL query
/*stmt = conn.createStatement();
String sql;
sql = "SELECT * FROM ingredient";
ResultSet rs = stmt.executeQuery(sql);*/
// Extract data from result set
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("ingredient_id");
String code = rs.getString("ingredient_code");
String description = rs.getString("ingredient_description");
//Display values
out.println("ID: " + id + "<br>");
out.println(", Code: " + code + "<br>");
out.println(", Description: " + description + "<br>");
}
out.println("</body></html>");
// Clean-up environment
rs.close();
statement.close();
connection.close();
} catch(SQLException se) {
//Handle errors for JDBC
se.printStackTrace();
} catch(Exception e) {
//Handle errors for Class.forName
e.printStackTrace();
} finally {
//finally block used to close resources
try {
if(statement!=null)
statement.close();
} catch(SQLException se2) {
} // nothing we can do
try {
if(connection!=null)
connection.close();
} catch(SQLException se) {
se.printStackTrace();
} //end finally try
} //end try
}
private Connection getConnection() {
Connection connection = null;
try {
/*InitialContext context = new InitialContext();
DataSource dataSource = (DataSource) context.lookup("jdbc/MYDB");
connection = dataSource.getConnection();*/
Context initContext = new InitialContext();
Context envContext = (Context)initContext.lookup("java:/comp/env");
DataSource ds = (DataSource)envContext.lookup("jdbc/MYDB");
connection = ds.getConnection();
} catch (NamingException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return connection;
}
}
下面示例中的url应该是url =“jdbc：mariadb：// localhost：3306 / MYDB”。在mariadb之后和//之前的JDBC URL中的冒号（:)丢失了。
<Resource name="jdbc/MYDB” auth="Container" type="javax.sql.DataSource"
maxTotal="100" maxIdle="30" maxWaitMillis="10000"
username="root" password="" driverClassName="org.mariadb.jdbc.Driver"
url="jdbc:mariadb//localhost:3306/MYDB”/>