要實現對數據庫的操作，離不開數據源（DataSource）或者連接（Connection）,但是通常來說對數據庫的操作都應該放在DAO中，而DAO又不應該與應用服務器相關聯，所以一般都使用連接（Connection）。現在我們這里就有一個問題了，怎么在攔截器中獲得連接。我想可以通過兩種方式獲得：
在分別討論這兩種方法之前，我們需要先討論一下在處理數據庫的時候的異常的處理。我這里做了一個TransactionException繼承至RuntimeException然后在攔截器里面拋出，再又應用框架處理這個異常。下面試這個類的代碼：
public class TransactionException extends RuntimeException {
private Throwable superException;
private String myMessage;
public TransactionException(Throwable throwable){
super(throwable);
this.superException = throwable;
}
public TransactionException(Throwable throwable,String message){
super(message,throwable);
this.superException = throwable;
this.myMessage = message;
}
/**
* @return Returns the myMessage.
*/
public String getMessage() {
return myMessage;
}
/**
* @return Returns the superException.
*/
public Throwable getSuperException() {
return superException;
}
/**
* @param myMessage The myMessage to set.
*/
public void setMyMessage(String message) {
this.myMessage = message;
}
/**
* @param superException The superException to set.
*/
public void setSuperException(Throwable superException) {
this.superException = superException;
}
}
1） 通過方法的第一個參數傳進去
l DAO
import java.sql.Connection;
public class TestDao {
public void insertA(Connection con,String a,String b,……){
…………………………………………
一系列操作
…………………………………………
}
public String queryA(Connection con,…….){
…………………………………………
一系列操作
…………………………………………
}
public void updateA(Connection con,…….){
…………………………………………
一系列操作
…………………………………………
}
}
l 攔截器
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class TransactionInterceptor implements Interceptor {
public void before(InvokeJniInfo invInfo) {
if(isNeedTransactions(invInfo)){
Connection conn = (Connection) invInfo.getArgs()[0];
try {
conn.setAutoCommit(false);
} catch (SQLException e) {
throw new TransactionException(e);
}
}
}
public void after(InvokeJniInfo invInfo) {
if(isNeedTransactions(invInfo)){
Connection conn = (Connection) invInfo.getArgs()[0];
try {
conn.commit();
} catch (SQLException e) {
throw new TransactionException(e);
}finally{
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
throw new TransactionException(e,"Close Connection is failure!");
}
}
}
}
}
public void exceptionThrow(InvokeJniInfo invInfo) {
if(isNeedTransactions(invInfo)){
Connection conn = (Connection) invInfo.getArgs()[0];
try {
conn.rollback();
} catch (SQLException e) {
throw new TransactionException(e);
}finally{
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
throw new TransactionException(e,"Close Connection is failure!");
}
}
}
}
}
private List getNeedTransaction(){
List needTransactions = new ArrayList();
needTransactions.add("insert");
needTransactions.add("update");
return needTransactions;
}
private boolean isNeedTransactions(InvokeJniInfo invInfo){
String needTransaction = "";
List needTransactions = getNeedTransaction();
for(int i = 0;i
needTransaction = (String)needTransactions.get(i);
if(invInfo.getMethod().getName().startsWith(needTransaction)){
return true;
}
}
return false;
}
}
需要注意的是：getNeedTransaction就是需要進行事務處理的方法的開頭，這個方法可以寫成一個從配置文件里面去讀，這里我就寫死在里面了。只是對insert和update開頭的方法進行事務控制。
2） 將Connection對象放在ThreadLocal中
l ConnectionUtil類：
import java.sql.Connection;
public final class ConnectionUtil {
private static ThreadLocal connections = new ThreadLocal();
public static Connection getConnection(){
Connection conn = null;
conn = (Connection) connections.get();
if(conn == null){
conn = getRealConnection();
connections.set(conn);
}
return conn;
}
public static void realseConnection(Connection conn){
connections.set(null);
}
private static Connection getRealConnection() {
實現自己獲取連接的代碼
return null;
}
}
l DAO類
public class TestDao {
public void insertA(String a,String b){
Connection conn = getConnection();
…………………………………………
一系列操作
…………………………………………
}
public String queryA(Connection con,…….){
Connection conn = getConnection();
…………………………………………
一系列操作
…………………………………………
}
public void updateA(Connection con,…….){
Connection conn = getConnection();
…………………………………………
一系列操作
…………………………………………
}
private Connection getConnection(){
return ConnectionUtil.getConnection();
}
}
l 攔截器
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class TransactionInterceptor implements Interceptor {
public void before(InvokeJniInfo invInfo) {
if(isNeedTransactions(invInfo)){
Connection conn = getConnection();
try {
conn.setAutoCommit(false);
} catch (SQLException e) {
throw new TransactionException(e);
}
}
}
public void after(InvokeJniInfo invInfo) {
if(isNeedTransactions(invInfo)){
Connection conn = getConnection();
try {
conn.commit();
} catch (SQLException e) {
throw new TransactionException(e);
}finally{
if(conn != null){
try {
conn.close();
releaseConnection(conn);
} catch (SQLException e) {
throw new TransactionException(e,"Close Connection is failure!");
}
}
}
}
}
public void exceptionThrow(InvokeJniInfo invInfo) {
if(isNeedTransactions(invInfo)){
Connection conn = getConnection();
try {
conn.rollback();
} catch (SQLException e) {
throw new TransactionException(e);
}finally{
if(conn != null){
try {
conn.close();
releaseConnection(conn);
} catch (SQLException e) {
throw new TransactionException(e,"Close Connection is failure!");
}
}
}
}
}
private Connection getConnection(){
return ConnectionUtil.getConnection();
}
private void releaseConnection(Connection conn){
ConnectionUtil.releaseConnection(conn);
}
private List getNeedTransaction(){
List needTransactions = new ArrayList();
needTransactions.add("insert");
needTransactions.add("update");
return needTransactions;
}
private boolean isNeedTransactions(InvokeJniInfo invInfo){
String needTransaction = "";
List needTransactions = getNeedTransaction();
for(int i = 0;i
needTransaction = (String)needTransactions.get(i);
if(invInfo.getMethod().getName().startsWith(needTransaction)){
return true;
}
}
return false;
}
}
最后將這個攔截器添加到AOP攔截框架中去，InterceptorHandler類中的getIntercetors方法中添加一個：
private synchronized List getIntercetors(){
if(null == interceptors){
interceptors = new ArrayList();
……………………………………
interceptors.add(new TransactionInterceptor ());
……………………………………
}
return interceptors;
}