There are many possible implementations of JDBC drivers. These implementations
are categorized as follows:
n Type 1 — drivers that implement the JDBC API as a mapping to another data
access API, such as ODBC. Drivers of this type are generally dependent on a
native library, which limits their portability. The JDBC-ODBC Bridge driver is an
example of a Type 1 driver.
n Type 2 — drivers that are written partly in the Java programming language and
partly in native code. These drivers use a native client library specific to the data
source to which they connect. Again, because of the native code, their portability
is limited.
n Type 3 — drivers that use a pure Java client and communicate with a middleware
server using a database-independent protocol. The middleware server then
communicates the client’s requests to the data source.
n Type 4 — drivers that are pure Java and implement the network protocol for a
specific data source. The client connects directly to the data source.
以上來自JDBC3.0的規(guī)范
Type1 用JDBC-ODBC bridge 來建立數(shù)據(jù)庫的connection，這種效率很一般，
public static Connection getConnectionbyBridge() {
Connection conn = null;
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
conn = DriverManager.getConnection("jdbc:odbc:abc", "cms", "cms");
System.out.println(conn.getTransactionIsolation());
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}
Typ2 是效率比較高的，部分用了jdbc的驅動，部分是要依賴數(shù)據(jù)庫的客戶端，比如ORACLE 10g OCI
public static Connection getConnectionOCI() {
Connection conn = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
conn = DriverManager.getConnection(
"jdbc:oracle:oci:@127.0.0.1:1521:orcl", "cms", "cms");
System.out.println(conn.getAutoCommit());
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}
Type3:網(wǎng)絡協(xié)議驅動 這種驅動實際上是根據(jù)我們熟悉的三層結構建立的. jdbc先把對數(shù)局庫的訪問請求傳遞給網(wǎng) 絡上的中間件服務器.
中間件服務器再把請求翻譯為符合數(shù)據(jù)庫規(guī)范的調用,再把這種調用
傳給數(shù)據(jù)庫服務器.如果中間件服務器也是用java開法的,那么在在中間層也可以使用1,2型 jdbc驅動程序作為訪問數(shù)據(jù)庫的方法.
網(wǎng)絡協(xié)議驅動---------中間件服務器------------數(shù)據(jù)庫Server
Type4 本地協(xié)議驅動
這種驅動直接把jdbc調用轉換為符合相關數(shù)據(jù)庫系統(tǒng)規(guī)范的請求.由于4型驅動寫的應用可 以直接和數(shù)據(jù)庫服務器通訊.這種類型的驅動完全由java實現(xiàn),因此實現(xiàn)了平臺獨立性. 本地協(xié)議驅動---------數(shù)據(jù)庫Server
public static Connection getConnection() {
Connection conn = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
conn = DriverManager.getConnection(
"jdbc:oracle:thin:@127.0.0.1:1521:orcl", "cms", "cms");
System.out.println(conn.getAutoCommit());
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}
對四種類型的jdbc驅動做了一個說明.那么它們適合那種類型的應用開發(fā)呢?
Jdbc-odbc橋由于它的執(zhí)行效率不高,更適合做為開發(fā)應用時的一種過度方案,或著對于初學 者了解jdbc編程也較適用.
對于那些需要大數(shù)據(jù)量操作的應用程序則應該考慮2,3,4型驅動.在intranet方面的應用可以 考慮2型驅動,而且目前開發(fā)
的趨勢是使用純java.所以3,4型驅動也可以作為考慮對象. 至于基于internet方面的應用就只有考慮3,4型驅動了.
因為3型驅動可以把多種數(shù)據(jù)庫驅 動都配置在中間層服務器.所以3型驅動最適合那種需要同時連接多個不同種類的數(shù)據(jù)庫, 并且對并發(fā)連接要求高的應用.
4型驅動則適合那些連接單一數(shù)據(jù)庫的工作組應用。
但是Typ2 和type1我認為很少會用到，type1 可移植，效率都不行，type2效率雖然高，但是可移植太差，只有3.4是最常用的,當然大規(guī)模的分布式應用3是很好的選擇，一般的企業(yè)應用，我認為用4就很夠了，并且效率也高。