我似乎無法從PLSQL

Question

調用java我有以下代碼（我試圖做的是從調用PLSQL Java代碼在google.com打開一個新的網頁）：

  CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "Hello" AS 
      import java.awt.Desktop; 
      import java.net.URI; 
      class Hello 
      { 
      public static void main(String args[]) throws Exception 
      { 
      Desktop d=Desktop.getDesktop(); 
      d.browse(new URI("http://google.com")); 
      } 
      }; 
      /

     CREATE OR REPLACE PROCEDURE SAMP_JAVA_CALL AS 
     LANGUAGE JAVA NAME 'Hello.main(java.lang.String[])'; 
     /

它編譯沒有任何錯誤，但是當我嘗試執行SAMP_JAVA_CALL過程中，我得到這個錯誤：

Error report - 
    ORA-29549: class JAYPV.Hello has changed, Java session state cleared 
    ORA-06512: at "JAYPV.SAMP_JAVA_CALL", line 1 
    ORA-06512: at line 1 
    29549. 00000 - "class %s.%s has changed, Java session state cleared" 
    *Cause: A class in use by the current session was redefined or dropped, 
      invalidating the current Java session state and requiring that 
      it be cleared. 
    *Action: No action required. 

你有這是爲什麼不工作的任何想法？ 我正在使用sqldeveloper版本4.0.0.13，Oracle版本12c。

Answer 1

ORA-29549: class ... has changed, Java session state cleared 

Cause: A class in use by the current session was redefined or dropped, invalidating the current Java session state and requiring that it be cleared.

「正常」方式，就可能出現這個錯誤是編譯Java對象在數據庫中並在同一個會話執行它。基本上當你改變java對象這會發生。 如果再次調用它，它將成功執行，結束會話，創建新會話也將起作用。

但是你可以使用一個技巧，我發現here。你可以發出在異常處理程序DBMS_JAVA.ENDSESSION_AND_RELATED_STATE來解決它，就像下面

DECLARE 
JAVA_SESSION_CLEARED EXCEPTION; 
PRAGMA EXCEPTION_INIT(JAVA_SESSION_CLEARED, -29549); 
-- 
V_KEEP_TRIES NUMBER := 3; 
V_TMP VARCHAR2(32000); 
BEGIN 
<<BEFORE_JAVA_CALL>> 
BEGIN 

JAVA_WRAPPER_PROC; 

EXCEPTION 
WHEN JAVA_SESSION_CLEARED THEN 
V_TMP := DBMS_JAVA.ENDSESSION_AND_RELATED_STATE; 
V_KEEP_TRIES := V_KEEP_TRIES - 1; 
IF V_KEEP_TRIES >= 0 THEN 
GOTO BEFORE_JAVA_CALL; 
ELSE 
RAISE; 
END IF; 
WHEN OTHERS THEN 
LM.SET_STATUS('FAILED', SQLERRM); 
RAISE; 
END;