BoneCP framework的整个框架设计，其实还是比较容易看懂的，大致用两天左右时间把源代码看了大概。
发现能够拿得出比较有意思的点应该是配置transactionRecoveryEnabled参数的意义，虽然在xml配置里面只是配置boolean类型true、false，但是内置的涵义挺有趣、挺cool。
了解transactionRecoveryEnabled参数首先需要把MemorizeTransactionProxy
public class MemorizeTransactionProxy implements InvocationHandler {
/** Target of proxy. */
private Object target;
/** Connection handle. Keep a WeakReference here because we want the GC to kick in if the application loses a handle on it.*/
private WeakReference<ConnectionHandle> connectionHandle;
/** List of methods that will trigger a reset of the transaction. */
private static final ImmutableSet<String> clearLogConditions = ImmutableSet.of("rollback", "commit", "close");
/** Class logger. */
private static final Logger logger = LoggerFactory.getLogger(MemorizeTransactionProxy.class);
/**
* Default constructor.
*/
public MemorizeTransactionProxy(){
// not needed
}
/** Wrap connection with a proxy.
* @param target connection handle
* @param connectionHandle originating bonecp connection
* @return Proxy to a connection.
*/
protected static Connection memorize(final Connection target, final ConnectionHandle connectionHandle) {
return (Connection) Proxy.newProxyInstance(
ConnectionProxy.class.getClassLoader(),
new Class[] {ConnectionProxy.class},
new MemorizeTransactionProxy(target, connectionHandle));
}
/** Wrap Statement with a proxy.
* @param target statement handle
* @param connectionHandle originating bonecp connection
* @return Proxy to a statement.
*/
protected static Statement memorize(final Statement target, final ConnectionHandle connectionHandle) {
return (Statement) Proxy.newProxyInstance(
StatementProxy.class.getClassLoader(),
new Class[] {StatementProxy.class},
new MemorizeTransactionProxy(target, connectionHandle));
}
/** Wrap PreparedStatement with a proxy.
* @param target statement handle
* @param connectionHandle originating bonecp connection
* @return Proxy to a Preparedstatement.
*/
protected static PreparedStatement memorize(final PreparedStatement target, final ConnectionHandle connectionHandle) {
return (PreparedStatement) Proxy.newProxyInstance(
PreparedStatementProxy.class.getClassLoader(),
new Class[] {PreparedStatementProxy.class},
new MemorizeTransactionProxy(target, connectionHandle));
}
/** Wrap CallableStatement with a proxy.
* @param target statement handle
* @param connectionHandle originating bonecp connection
* @return Proxy to a Callablestatement.
*/
protected static CallableStatement memorize(final CallableStatement target, final ConnectionHandle connectionHandle) {
return (CallableStatement) Proxy.newProxyInstance(
CallableStatementProxy.class.getClassLoader(),
new Class[] {CallableStatementProxy.class},
new MemorizeTransactionProxy(target, connectionHandle));
}
/** Main constructor
* @param target target to actual handle
* @param connectionHandle bonecp ref
*/
private MemorizeTransactionProxy(Object target, ConnectionHandle connectionHandle) {
this.target = target;
this.connectionHandle = new WeakReference<ConnectionHandle>(connectionHandle);
}
// @Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Object result = null;
ConnectionHandle con = this.connectionHandle.get();
if (con != null){ // safety!
if (method.getName().equals("getProxyTarget")){ // special "fake" method to return our proxy target
return this.target;
}
if (con.isInReplayMode()){ // go straight through when flagged as in playback (replay) mode.
try{
return method.invoke(this.target, args);
} catch (InvocationTargetException t){
throw t.getCause(); // we tried running it, but playback mode also blew up. Throw out the cause, not the
// wrapped invocationtargetexception.
}
}
if (con.recoveryResult != null){ // if we previously failed, do the mapping to the new connection/statements
Object remap = con.recoveryResult.getReplaceTarget().get(this.target);
if (remap != null){
this.target = remap;
}
remap = con.recoveryResult.getReplaceTarget().get(con);
if (remap != null){
con = (ConnectionHandle) remap;
}
}
// record this invocation
if (!con.isInReplayMode() && !method.getName().equals("hashCode")
&& !method.getName().equals("equals") && !method.getName().equals("toString")){
con.getReplayLog().add(new ReplayLog(this.target, method, args));
}
try{
// run and swap with proxies if we encounter prepareStatement calls
result = runWithPossibleProxySwap(method, this.target, args);
// when we commit/close/rollback, destroy our log. Does this work if we have nested transactions???? Fixme?
if (!con.isInReplayMode() && (this.target instanceof Connection) && clearLogConditions.contains(method.getName())){
con.getReplayLog().clear();
// con.recoveryResult.getReplaceTarget().clear();
}
} catch (Throwable t){
// if we encounter problems, grab a connection and replay back our log
List<ReplayLog> oldReplayLog = con.getReplayLog();
con.setInReplayMode(true); // stop recording
// this will possibly terminate all connections here
if (t instanceof SQLException || (t.getCause() != null && t.getCause() instanceof SQLException)){
con.markPossiblyBroken((SQLException)t.getCause());
}
if (!con.isPossiblyBroken()){ // connection is possibly recoverable...
con.setInReplayMode(false); // start recording again
con.getReplayLog().clear();
} else { // connection is possibly recoverable...
logger.error("Connection failed. Attempting to recover transaction on Thread #"+ Thread.currentThread().getId());
// let's try and recover
try{
con.recoveryResult = attemptRecovery(oldReplayLog); // this might also fail
con.setReplayLog(oldReplayLog); // attemptRecovery will probably destroy our original connection handle
con.setInReplayMode(false); // start recording again
logger.error("Recovery succeeded on Thread #" + Thread.currentThread().getId());
con.possiblyBroken = false;
// return the original result the application was expecting
return con.recoveryResult.getResult();
} catch(Throwable t2){
con.setInReplayMode(false); // start recording again
con.getReplayLog().clear();
/* #ifdef JDK6
throw new SQLException("Could not recover transaction.", t.getCause());
#endif JDK6 */
/* #ifdef JDK5
throw new SQLException("Could not recover transaction. Original exception follows." + t.getCause());
#endif JDK5 */
}
}
// it must some user-level error eg setting a preparedStatement parameter that is out of bounds. Just throw it back to the user.
throw t.getCause();
}
}
return result; // normal state
}
/** Runs the given method with the specified arguments, substituting with proxies where necessary
* @param method
* @param target proxy target
* @param args
* @return Proxy-fied result for statements, actual call result otherwise
* @throws IllegalAccessException
* @throws InvocationTargetException
*/
private Object runWithPossibleProxySwap(Method method, Object target, Object[] args)
throws IllegalAccessException, InvocationTargetException {
Object result;
// swap with proxies to these too.
if (method.getName().equals("createStatement")){
result = memorize((Statement)method.invoke(target, args), this.connectionHandle.get());
}
else if (method.getName().equals("prepareStatement")){
result = memorize((PreparedStatement)method.invoke(target, args), this.connectionHandle.get());
}
else if (method.getName().equals("prepareCall")){
result = memorize((CallableStatement)method.invoke(target, args), this.connectionHandle.get());
}
else result = method.invoke(target, args);
return result;
}
/** Play back a transaction
* @param oldReplayLog
* @return map + result
* @throws SQLException
*
*/
private TransactionRecoveryResult attemptRecovery(List<ReplayLog> oldReplayLog) throws SQLException{
boolean tryAgain = false;
Throwable failedThrowable = null;
ConnectionHandle con = this.connectionHandle.get();
if (con == null){ // safety!
throw PoolUtil.generateSQLException("ConnectionHandle is gone!", new IllegalStateException());
}
TransactionRecoveryResult recoveryResult = con.recoveryResult;
ConnectionHook connectionHook = con.getPool().getConfig().getConnectionHook();
int acquireRetryAttempts = con.getPool().getConfig().getAcquireRetryAttempts();
long acquireRetryDelay = con.getPool().getConfig().getAcquireRetryDelayInMs();
AcquireFailConfig acquireConfig = new AcquireFailConfig();
acquireConfig.setAcquireRetryAttempts(new AtomicInteger(acquireRetryAttempts));
acquireConfig.setAcquireRetryDelayInMs(acquireRetryDelay);
acquireConfig.setLogMessage("Failed to replay transaction");
Map<Object, Object> replaceTarget = new HashMap<Object, Object>();
do{
replaceTarget.clear();
// make a copy
for (Entry<Object, Object> entry: recoveryResult.getReplaceTarget().entrySet()){
replaceTarget.put(entry.getKey(), entry.getValue());
}
List<PreparedStatement> prepStatementTarget = new ArrayList<PreparedStatement>();
List<CallableStatement> callableStatementTarget = new ArrayList<CallableStatement>();
List<Statement> statementTarget = new ArrayList<Statement>();
Object result = null;
tryAgain = false;
// this connection is dead
con.setInReplayMode(true); // don't go in a loop of saving our saved log!
try{
con.clearStatementCaches(true);
con.getInternalConnection().close();
} catch(Throwable t){
// do nothing - also likely to fail here
}
try{
con.setInternalConnection(memorize(con.getPool().obtainInternalConnection(con), con));
} catch(SQLException e){
throw con.markPossiblyBroken(e);
}
con.getOriginatingPartition().trackConnectionFinalizer(con); // track this too.
for (ReplayLog replay: oldReplayLog){
// we got new connections/statement handles so replace what we've got with the new ones
if (replay.getTarget() instanceof Connection){
replaceTarget.put(replay.getTarget(), con.getInternalConnection());
} else if (replay.getTarget() instanceof CallableStatement){
if (replaceTarget.get(replay.getTarget()) == null){
replaceTarget.put(replay.getTarget(), callableStatementTarget.remove(0));
}
} else if (replay.getTarget() instanceof PreparedStatement){
if (replaceTarget.get(replay.getTarget()) == null){
replaceTarget.put(replay.getTarget(), prepStatementTarget.remove(0));
}
}else if (replay.getTarget() instanceof Statement){
if (replaceTarget.get(replay.getTarget()) == null){
replaceTarget.put(replay.getTarget(), statementTarget.remove(0));
}
}
try {
// run again using the new connection/statement
// result = replay.getMethod().invoke(, replay.getArgs());
result = runWithPossibleProxySwap(replay.getMethod(), replaceTarget.get(replay.getTarget()), replay.getArgs());
// remember what we've got last
recoveryResult.setResult(result);
// if we got a new statement (eg a prepareStatement call), save it, we'll use it for our search/replace
if (result instanceof CallableStatement){
callableStatementTarget.add((CallableStatement)result);
} else if (result instanceof PreparedStatement){
prepStatementTarget.add((PreparedStatement)result);
} else if (result instanceof Statement){
statementTarget.add((Statement)result);
}
} catch (Throwable t) {
// It blew up again, let's try a couple more times before giving up...
// call the hook, if available.
if (connectionHook != null){
tryAgain = connectionHook.onAcquireFail(t, acquireConfig);
} else {
logger.error("Failed to replay transaction. Sleeping for "+acquireRetryDelay+"ms and trying again. Attempts left: "+acquireRetryAttempts+". Exception: "+t.getCause() + " Message:"+t.getMessage());
try {
Thread.sleep(acquireRetryDelay);
if (acquireRetryAttempts > 0){
tryAgain = (--acquireRetryAttempts) != 0;
}
} catch (InterruptedException e) {
tryAgain=false;
}
}
if (!tryAgain){
failedThrowable = t;
}
break;
}
}
} while (tryAgain);
// fill last successful results
for (Entry<Object, Object> entry: replaceTarget.entrySet()){
recoveryResult.getReplaceTarget().put(entry.getKey(), entry.getValue());
}
for (ReplayLog replay: oldReplayLog){
replay.setTarget(replaceTarget.get(replay.getTarget())); // fix our log
}
if (failedThrowable != null){
throw PoolUtil.generateSQLException(failedThrowable.getMessage(), failedThrowable);
}
return recoveryResult;
}
}
其实就是类似于录影功能，通过代理方式，重新播放一次操作，有没有觉得其实我们可以把类似的想法放到我们开发中，诸如：短信邮件的发送、重复性动作的模仿操作......