java JDBC 无法连接到 openshift 上的 mysql 数据库
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JDBC can't connect to mysql database on openshift
提问by W.K.S
I managed to set up MySQL database on OpenShift with phpMyAdmin and all. I was told the host name and port my for my database are $OPENSHIFT_MYSQL_DB_HOST and $OPENSHIFT_MYSQL_DB_PORT respectively, which I put in my context.xml file like this:
我设法使用 phpMyAdmin 在 OpenShift 上设置了 MySQL 数据库。有人告诉我，我的数据库的主机名和端口分别是 $OPENSHIFT_MYSQL_DB_HOST 和 $OPENSHIFT_MYSQL_DB_PORT，我将它们放入我的 context.xml 文件中，如下所示：
<context-param>
<param-name>driver</param-name>
<param-value>com.mysql.jdbc.Driver</param-value>
</context-param>
<context-param>
<param-name>url</param-name>
<param-value>jdbc:mysql://$OPENSHIFT_MYSQL_DB_HOST:$OPENSHIFT_MYSQL_DB_PORT/burgerjoint</param-value>
</context-param>
<context-param>
<param-name>user</param-name>
<param-value>admin******</param-value>
</context-param>
<context-param>
<param-name>password</param-name>
<param-value>*********</param-value>
</context-param>
The code to set up the connection is:
建立连接的代码是：
public void contextInitialized(ServletContextEvent event) {
// Connect
String driver = event.getServletContext().getInitParameter(PARAM_DRIVER);
String url = event.getServletContext().getInitParameter(PARAM_URL);
String username = event.getServletContext().getInitParameter(PARAM_USERNAME);
String password = event.getServletContext()
.getInitParameter(PARAM_PASSWORD);
try {
Class.forName(driver);
Connection connection = DriverManager.getConnection(url, username,
password);
event.getServletContext().setAttribute(ATTR_CONNECTION, connection);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
but the problem is that the connection is null on the server and I don't understand why. Did I do something wrong? The code works when I try it on localhost. And as far as I can tell, I have all necessary libraries:
但问题是服务器上的连接为空，我不明白为什么。我做错什么了吗？当我在本地主机上尝试时，该代码有效。据我所知，我拥有所有必要的库：
Thanks for the help :)
谢谢您的帮助 ：）
Update
更新
I've modified the Connection code as follows:
我修改了连接代码如下：
{
if (connection != null) return connection;
try
{
Properties dbProperties = new Properties();
InputStream input = DatabaseUtil.class.getClassLoader().getResourceAsStream(DB_PROPERTIES_FILE);
dbProperties.load(input);
String url = "";
if (appIsDeployed)
{
String host = System.getenv("$OPENSHIFT_MYSQL_DB_HOST");
String port = System.getenv("$OPENSHIFT_MYSQL_DB_PORT");
String name = "burgerjoint";
url = "jdbc:mysql://" + host + ":" + port + "/" + name;
} else
{
url = dbProperties.getProperty(PARAM_URL);
}
String driver = dbProperties.getProperty(PARAM_DRIVER);
String username = dbProperties.getProperty(PARAM_USERNAME);
String password = dbProperties.getProperty(PARAM_PASSWORD);
Class.forName(driver);
connection = DriverManager.getConnection(url, username, password);
but it still gives null connection. The values of System.getenv("$OPENSHIFT_MYSQL_DB_HOST")and System.getenv("$OPENSHIFT_MYSQL_DB_PORT")are null.
但它仍然提供空连接。的值System.getenv("$OPENSHIFT_MYSQL_DB_HOST")和System.getenv("$OPENSHIFT_MYSQL_DB_PORT")空。
采纳答案by duffymo
This is incorrect:
这是不正确的：
jdbc:mysql://$OPENSHIFT_MYSQL_DB_HOST:$OPENSHIFT_MYSQL_DB_PORT/burgerjoint
That dollar sign suggests that you think a proper host and database name will be substituted, but that's not the case.
该美元符号表明您认为将替换正确的主机和数据库名称，但事实并非如此。
Code the host and database name to see that it works, then learn about .properties files to externalize it.
编码主机和数据库名称以查看它是否有效，然后了解 .properties 文件以将其外部化。
回答by JAN
Remove the Dollar signs :
删除美元符号：
String host = System.getenv("OPENSHIFT_MYSQL_DB_HOST");
String port = System.getenv("OPENSHIFT_MYSQL_DB_PORT");
And it will work great (I tested it on my machine and on my OpenShift) .
它会很好用（我在我的机器和我的 OpenShift 上测试过）。
回答by Paul Vargas
If you are using the MySQL cartridge, the information to connect to the database are in the environment variablesof the application. If you are using JDBC pure , you need to first retrieve the values??. e.g.:
如果您使用的是 MySQL 卡夹，则连接到数据库的信息在应用程序的环境变量中。如果您使用 JDBC pure ，您需要首先检索值？？。例如：
String host = System.getenv("OPENSHIFT_MYSQL_DB_HOST");
String port = System.getenv("OPENSHIFT_MYSQL_DB_PORT");
String username = System.getenv("OPENSHIFT_MYSQL_DB_USERNAME");
String password = System.getenv("OPENSHIFT_MYSQL_DB_PASSWORD");
String url = String.format(":mysql://%s:%s/jbossas", host, port);
Connection conn = DriverManager.getConnection(url, username, password);
The jbossasin the string url is the schema. Change with your schema (burgerjoint).
该jbossas字符串中URL是架构。随您的架构 ( burgerjoint) 进行更改。
回答by Ashish Chougule
Can you please try to start port-forwarding first.
您能否先尝试启动端口转发。
rhc port-forward -a your-app-name
rhc port-forward -a your-app-name
Once started don't kill this cmd & just use the generated local addresses/ports.
启动后不要终止此 cmd，只需使用生成的本地地址/端口即可。
