我無法連接來自Netbeans的數據庫

Question

我在互聯網上有一個MySQL數據庫。我可以通過瀏覽器和MySQL Workbench成功訪問它。我將數據庫添加到Netbeans。當我試圖從數據庫連接Netbeans的我得到這個錯誤：

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException 
Error code 0, SQL state 08S01: Communications link failure 

The last packet successfully received from the server was 14.047 milliseconds ago. The last packet sent successfully to the server was 1 milliseconds ago. 

我也試圖通過使用RESTful Web服務連接數據庫。我得到這個錯誤：

GET RequestFailed RequestFailed --> Status: (500) 
Response: { 
HTTP Status 500 - 

type Exception report 

message 

descriptionThe server encountered an internal error() that prevented it from fulfilling this request. 

exception 

javax.servlet.ServletException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.DatabaseException 
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed. 
Error Code: 0 
Call: SELECT o_id, isim, not, yas FROM ogrenci 
Query: ReadAllQuery(referenceClass=Ogrenci sql="SELECT o_id, isim, not, yas FROM ogrenci") 
root cause 

Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.DatabaseException 
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed. 
Error Code: 0 
Call: SELECT o_id, isim, not, yas FROM ogrenci 
Query: ReadAllQuery(referenceClass=Ogrenci sql="SELECT o_id, isim, not, yas FROM ogrenci") 
root cause 

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed. 
root cause 

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure 

The last packet successfully received from the server was 228.471 milliseconds ago. The last packet sent successfully to the server was 11 milliseconds ago. 
root cause 

java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost. 
note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 3.1.2.2 logs. 

Answer 1

儘量加大wait_timeout mysql的變量：

SET wait_timeout=300;