透過 JDBC 連線 Oracle 資料庫

要透過 Java JDBC 連線至 Oracle 資料庫，有幾個要注意的地方：

首先搞清楚連線對象是 "SID" 或 "Service Name" 因為兩者使用語法並不相同，其中：

1. SID (unique name of the INSTANCE)

jdbc:oracle:thin:[USER/PASSWORD]@[HOST][:PORT]:SID

2. Service Name (Alias to an INSTANCE)

jdbc:oracle:thin:[USER/PASSWORD]@//[HOST][:PORT]/SERVICE

實際例子：

Connection conn = null;
conn = DriverManager.getConnection
       ("jdbc:oracle:thin:ID/PASS//HOST_IP:1521/SERVICE_NAME"); 

再來，包裝你想送出的查詢

String StrX = "SELECT * FROM FOO";
sqlMsg = sqlMsg + "WHERE BAR=15";

Statement myQuery = conn.createStatement();
ResultSet Output = myQuery.executeQuery(sqlMsg);

while( Output.next() ) /* 透過迴圈取得資料 */
{
  System.out.println ( 
    Output.getString(1) + "," + Output.getString(2)+ "," +
    Output.getString(3) + "," + Output.getString(4)
  );
}

Output.close();
myQuery.close();
conn.close();

最後必須有一段程式碼，來處理例外狀況 (Java編譯時會偵測)

catch (ClassNotFoundException e) 
{ 
  System.err.println(e.getMessage()); 
}
catch (SQLException e) 
{ 
  System.err.println(e.getMessage()); 
} 
finally 
{ 
  try 
  { 
    if(conn != null) 
      conn.close(); 
  } 
  catch(SQLException e) 
  { 
    System.err.println(e); 
  } 
} 

--

有關 Java 8 中 java.sql.* 函式庫的變革：

The JDBC 4.2 API includes both the java.sql package, referred to as the JDBC core API, and the javax.sql package, referred to as the JDBC Optional Package API. This complete JDBC API is included in the Java Standard Edition (Java SE), version 7.

Since 1.8 -- new in the JDBC 4.2 API and part of the Java SE platform, version 8
Since 1.7 -- new in the JDBC 4.1 API and part of the Java SE platform, version 7

然後最重要的是從 JDBC 4.0 起，不需透過 Class.forName() 預先註冊 Driver
auto java.sql.Driver discovery - no longer need to load a java.sql.Driver class via Class.forName

編譯與執行 (工作目錄 c:\project)

> 編譯 javac foo.java
> 執行 java -cp "c:\project;c:\project\ojdbc8\ojdbc8.jar" foo