一次执行一次,ServletContextListener
而不是每次在init()
许多servlet中执行一次。contextInitialized()
在webapp启动期间,该方法仅执行一次。
public class Config implements servletcontextlistener {
private static final String ATTRIBUTE_NAME = "config";
private DataSource dataSource;
@Override
public void contextInitialized(ServletContextEvent event) {
ServletContext servletContext = event.getServletContext();
String databaseName = servletContext.getInitParameter("database.name");
try {
dataSource = (DataSource) new InitialContext().lookup(databaseName);
} catch (NamingException e) {
throw new RuntimeException("Config Failed: datasource not found", e);
}
servletContext.setAttribute(ATTRIBUTE_NAME, this);
}
@Override
public void contextDestroyed(ServletContextEvent event) {
// NOOP.
}
public DataSource getDataSource() {
return dataSource;
}
public static Config getInstance(ServletContext servletContext) {
return (Config) servletContext.getAttribute(ATTRIBUTE_NAME);
}
}
在中进行如下配置web.xml
:
<context-param>
<param-name>database.name</param-name>
<param-value>jdbc/MysqLdb</param-value>
</context-param>
<listener>
<listener-class>com.example.Config</listener-class>
</listener>
您可以按以下方式在servlet中获取它(init()
或doXXX()
选择方法):
DataSource dataSource = Config.getInstance(getServletContext()).getDataSource();
但是,我将进一步重构它,最好将JDBC代码放在其自己的类中,而不是在servlet中。查找DAO模式。