tomcat8主java HttpServlet工作，但ServletContextListener无法访问mysql数据库
我正在使用ubuntu 16.04、tomcat8、mysql 5.7.12和activeMQ做一些事情。我在谷歌上搜索了很多。我通常找不到关于我的具体情况的例子，但通常是针对较旧的tomcat和mysql版本，等等。我基本上是在上下文侦听器工作时（每隔15分钟检查一次特定的活动）出现这个错误的。我正在使用IntelliJ社区版和maven
javax.naming.NameNotFoundException: Name [comp/env/jdbc/acnn] is not bound in this Context. Unable to find [comp].
at org.apache.naming.NamingContext.lookup(NamingContext.java:819)
at org.apache.naming.NamingContext.lookup(NamingContext.java:166)
at org.apache.naming.SelectorContext.lookup(SelectorContext.java:157)
at javax.naming.InitialContext.lookup(InitialContext.java:417)
at org.davidliebman.desktop.audio.ACNNDataBase.getConnection(ACNNDataBase.java:87)
at org.davidliebman.desktop.audio.ACNNDataBase.doUpdate(ACNNDataBase.java:199)
at org.davidliebman.desktop.audio.ACNNDataBase.deleteUserPlaying(ACNNDataBase.java:386)
at org.davidliebman.server.audio.ACNNContextListener$DB.run(ACNNContextListener.java:39)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)
java.lang.NullPointerException
“acnn”是我的数据库的名称。下面是我的网站。我的战争中的xml文件：
<web-app
xmlns="http://java.sun.com/xml/ns/javaee"
metadata-complete="false"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1">
<servlet>
<servlet-name>ACNNServer</servlet-name>
<servlet-class>org..server.audio.ACNNServer</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ACNNServer</servlet-name>
<url-pattern>/ACNNServer</url-pattern>
</servlet-mapping>
<listener>
<listener-class>
org..server.audio.ACNNContextListener
</listener-class>
</listener>
<resource-ref>
<description>ACNN DB</description>
<res-ref-name>jdbc/acnn</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
</web-app>
这是我的conf/server部分。xml
<GlobalNamingResources>
<!-- Editable user database that can also be used by
UserDatabaseRealm to authenticate users
-->
<Resource name="UserDatabase" auth="Container"
type="org.apache.catalina.UserDatabase"
description="User database that can be updated and saved"
factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
pathname="conf/tomcat-users.xml" />
<Resource name="jdbc/acnn" auth="Container" type="javax.sql.DataSource"
maxTotal="100" maxIdle="30" maxWaitMillis="10000"
username="xxx" password="xxx" driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/acnn"
removeAbandonedOnBorrow="true"
removeAbandonedOnMaintenance="true"
removeAbandonedTimeout="60"
logAbandoned="true" />
<ResourceLink name="jdbc/acnn"
global="jdbc/acnn"
type="javax.sql.DataSource" />
</GlobalNamingResources>
下面是conf/context的匹配部分。xml文件
<Context allowLinking="true">
<WatchedResource>WEB-INF/web.xml</WatchedResource>
<WatchedResource>${catalina.base}/conf/web.xml</WatchedResource>
<Resource name="jdbc/acnn" auth="Container" type="javax.sql.DataSource"
maxTotal="100" maxIdle="30" maxWaitMillis="10000"
username="xxx" password="xxx" driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/acnn"
removeAbandonedOnBorrow="true"
removeAbandonedOnMaintenance="true"
removeAbandonedTimeout="60"
logAbandoned="true" />
<ResourceLink name="jdbc/acnn"
global="jdbc/acnn"
type="javax.sql.DataSource" />
</Context>
最后，我将材料复制到META-INF/上下文中。xml文件。我认为它被忽略了。不确定
<Context allowLinking="true">
<WatchedResource>WEB-INF/web.xml</WatchedResource>
<WatchedResource>${catalina.base}/conf/web.xml</WatchedResource>
<Resource name="jdbc/acnn" auth="Container" type="javax.sql.DataSource"
maxTotal="100" maxIdle="30" maxWaitMillis="10000"
username="xxx" password="xxx" driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/acnn"
removeAbandonedOnBorrow="true"
removeAbandonedOnMaintenance="true"
removeAbandonedTimeout="60"
logAbandoned="true" />
<ResourceLink name="jdbc/acnn"
global="jdbc/acnn"
type="javax.sql.DataSource" />
</Context>
当从HttpServlet而不是从ServletContextListener运行时，实际代码如下所示：
public class ACNNDataBase {
...
private Connection getConnection() {
Connection conn = null;
try {
InitialContext ctx = new InitialContext();
DataSource ds = (DataSource) ctx.lookup("java:comp/env/jdbc/acnn");
conn = ds.getConnection();
}
catch (Exception e) { e.printStackTrace();}
return conn;
}
public void getVersion() {
String command = "SELECT VERSION()";
String rs = doQuery(command);
System.out.println(rs);
}
public String doQuery(String command) {
try {
Connection con = getConnection();
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(command);
String value = "";
while (rs.next()) {
System.out.println(rs.getString(1));
value = rs.getString(1);
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
if (rs != null) {
rs.close();
}
if (st != null) {
st.close();
}
if (con != null) {
con.close();
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
return value;
}
...
}
下面是调用db函数的类：
public class ACNNContextListener implements ServletContextListener{
private int FIFTEEN_MINUTES = 15;
public void contextInitialized(ServletContextEvent servletContextEvent) {
Timer timer = new Timer(true);
timer.scheduleAtFixedRate(new DB(), 0, FIFTEEN_MINUTES * 60 * 1000);
}
public void contextDestroyed(ServletContextEvent servletContextEvent) {
}
class DB extends TimerTask{
public void run () {
ACNNDataBase db = new ACNNDataBase();
db.getVersion();
}
}
}
就这些。任何帮助都将不胜感激。谢谢
# 1 楼答案
我刚刚在我的机器上测试了它，主要技巧是：
详细信息： 您只需执行以下操作：
-为配置只保留
META-INF/context.xml-将节保留在
web.xml中-从tomcat/conf/web中删除所有配置（将其恢复为默认值）。xml，tomcat/conf/server。xml和tomcat/conf/context。xml
-在侦听器中，获取连接，如本例所示：
我的完整META-INF/context。xml: