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本文主要研究一下druid的handleException
prepareStatement
com/alibaba/druid/pool/DruidPooledConnection.java
代码语言：javascript复制 public PreparedStatement prepareStatement(String sql) throws SQLException {
checkState();
PreparedStatementHolder stmtHolder = null;
PreparedStatementKey key = new PreparedStatementKey(sql, getCatalog(), MethodType.M1);
boolean poolPreparedStatements = holder.isPoolPreparedStatements();
if (poolPreparedStatements) {
stmtHolder = holder.getStatementPool().get(key);
}
if (stmtHolder == null) {
try {
stmtHolder = new PreparedStatementHolder(key, conn.prepareStatement(sql));
holder.getDataSource().incrementPreparedStatementCount();
} catch (SQLException ex) {
handleException(ex, sql);
}
}
initStatement(stmtHolder);
DruidPooledPreparedStatement rtnVal = new DruidPooledPreparedStatement(this, stmtHolder);
holder.addTrace(rtnVal);
return rtnVal;
}DruidPooledConnection的prepareStatement会catch住SQLException然后执行handleException
executeQuery
com/alibaba/druid/pool/DruidPooledPreparedStatement.java
代码语言：javascript复制 public ResultSet executeQuery() throws SQLException {
checkOpen();
incrementExecuteQueryCount();
transactionRecord(sql);
oracleSetRowPrefetch();
conn.beforeExecute();
try {
ResultSet rs = stmt.executeQuery();
if (rs == null) {
return null;
}
DruidPooledResultSet poolableResultSet = new DruidPooledResultSet(this, rs);
addResultSetTrace(poolableResultSet);
return poolableResultSet;
} catch (Throwable t) {
errorCheck(t);
throw checkException(t);
} finally {
conn.afterExecute();
}
}executeQuery在catch到Throwable时会执行throw checkException(t)
checkException
com/alibaba/druid/pool/DruidPooledStatement.java
代码语言：javascript复制 protected SQLException checkException(Throwable error) throws SQLException {
String sql = null;
if (this instanceof DruidPooledPreparedStatement) {
sql = ((DruidPooledPreparedStatement) this).getSql();
}
handleSocketTimeout(error);
exceptionCount ;
return conn.handleException(error, sql);
}checkException这里会执行conn.handleException(error, sql)
handleException
代码语言：javascript复制 public SQLException handleException(Throwable t, String sql) throws SQLException {
final DruidConnectionHolder holder = this.holder;
//
if (holder != null) {
DruidAbstractDataSource dataSource = holder.getDataSource();
dataSource.handleConnectionException(this, t, sql);
}
if (t instanceof SQLException) {
throw (SQLException) t;
}
throw new SQLException("Error", t);
}handleException这里是委托给了dataSource.handleConnectionException(this, t, sql);
handleConnectionException
com/alibaba/druid/pool/DruidDataSource.java
代码语言：javascript复制 public void handleConnectionException(DruidPooledConnection pooledConnection,
Throwable t,
String sql) throws SQLException {
final DruidConnectionHolder holder = pooledConnection.getConnectionHolder();
if (holder == null) {
return;
}
errorCountUpdater.incrementAndGet(this);
lastError = t;
lastErrorTimeMillis = System.currentTimeMillis();
if (t instanceof SQLException) {
SQLException sqlEx = (SQLException) t;
// broadcastConnectionError
ConnectionEvent event = new ConnectionEvent(pooledConnection, sqlEx);
for (ConnectionEventListener eventListener : holder.getConnectionEventListeners()) {
eventListener.connectionErrorOccurred(event);
}
// exceptionSorter.isExceptionFatal
if (exceptionSorter != null && exceptionSorter.isExceptionFatal(sqlEx)) {
handleFatalError(pooledConnection, sqlEx, sql);
}
throw sqlEx;
} else {
throw new SQLException("Error", t);
}
}handleConnectionException方法在exceptionSorter.isExceptionFatal(sqlEx)为true时会执行handleFatalError
isExceptionFatal
com/alibaba/druid/pool/vendor/MySqlExceptionSorter.java
代码语言：javascript复制public class MySqlExceptionSorter implements ExceptionSorter {
@Override
public boolean isExceptionFatal(SQLException e) {
if (e instanceof SQLRecoverableException) {
return true;
}
final String sqlState = e.getSQLState();
final int errorCode = e.getErrorCode();
if (sqlState != null && sqlState.startsWith("08")) {
return true;
}
switch (errorCode) {
// Communications Errors
case 1040: // ER_CON_COUNT_ERROR
case 1042: // ER_BAD_HOST_ERROR
case 1043: // ER_HANDSHAKE_ERROR
case 1047: // ER_UNKNOWN_COM_ERROR
case 1081: // ER_IPSOCK_ERROR
case 1129: // ER_HOST_IS_BLOCKED
case 1130: // ER_HOST_NOT_PRIVILEGED
// Authentication Errors
case 1045: // ER_ACCESS_DENIED_ERROR
// Resource errors
case 1004: // ER_CANT_CREATE_FILE
case 1005: // ER_CANT_CREATE_TABLE
case 1015: // ER_CANT_LOCK
case 1021: // ER_DISK_FULL
case 1041: // ER_OUT_OF_RESOURCES
// Out-of-memory errors
case 1037: // ER_OUTOFMEMORY
case 1038: // ER_OUT_OF_SORTMEMORY
// Access denied
case 1142: // ER_TABLEACCESS_DENIED_ERROR
case 1227: // ER_SPECIFIC_ACCESS_DENIED_ERROR
case 1023: // ER_ERROR_ON_CLOSE
case 1290: // ER_OPTION_PREVENTS_STATEMENT
return true;
default:
break;
}
// for oceanbase
if (errorCode >= -9000 && errorCode <= -8000) {
return true;
}
String className = e.getClass().getName();
if (className.endsWith(".CommunicationsException")) {
return true;
}
String message = e.getMessage();
if (message != null && message.length() > 0) {
if (message.startsWith("Streaming result set com.mysql.jdbc.RowDataDynamic")
&& message.endsWith("is still active. No statements may be issued when any streaming result sets are open and in use on a given connection. Ensure that you have called .close() on any active streaming result sets before attempting more queries.")) {
return true;
}
final String errorText = message.toUpperCase();
if ((errorCode == 0 && (errorText.contains("COMMUNICATIONS LINK FAILURE")) //
|| errorText.contains("COULD NOT CREATE CONNECTION")) //
|| errorText.contains("NO DATASOURCE") //
|| errorText.contains("NO ALIVE DATASOURCE")) {
return true;
}
}
Throwable cause = e.getCause();
for (int i = 0; i < 5 && cause != null; i) {
if (cause instanceof SocketTimeoutException) {
return true;
}
className = cause.getClass().getName();
if (className.endsWith(".CommunicationsException")) {
return true;
}
cause = cause.getCause();
}
return false;
}
@Override
public void configFromProperties(Properties properties) {
}
}MySqlExceptionSorter针对指定错误码来判断是否fatal
handleFatalError
com/alibaba/druid/pool/DruidDataSource.java
代码语言：javascript复制 protected final void handleFatalError(DruidPooledConnection conn,
SQLException error,
String sql) throws SQLException {
final DruidConnectionHolder holder = conn.holder;
if (conn.isTraceEnable()) {
activeConnectionLock.lock();
try {
if (conn.isTraceEnable()) {
activeConnections.remove(conn);
conn.setTraceEnable(false);
}
} finally {
activeConnectionLock.unlock();
}
}
long lastErrorTimeMillis = this.lastErrorTimeMillis;
if (lastErrorTimeMillis == 0) {
lastErrorTimeMillis = System.currentTimeMillis();
}
if (sql != null && sql.length() > 1024) {
sql = sql.substring(0, 1024);
}
boolean requireDiscard = false;
final ReentrantLock lock = conn.lock;
lock.lock();
try {
if ((!conn.isClosed()) || !conn.isDisable()) {
conn.disable(error);
requireDiscard = true;
}
lastFatalErrorTimeMillis = lastErrorTimeMillis;
fatalErrorCount ;
if (fatalErrorCount - fatalErrorCountLastShrink > onFatalErrorMaxActive) {
onFatalError = true;
}
lastFatalError = error;
lastFatalErrorSql = sql;
} finally {
lock.unlock();
}
if (onFatalError && holder != null && holder.getDataSource() != null) {
ReentrantLock dataSourceLock = holder.getDataSource().lock;
dataSourceLock.lock();
try {
emptySignal();
} finally {
dataSourceLock.unlock();
}
}
if (requireDiscard) {
if (holder.statementTrace != null) {
holder.lock.lock();
try {
for (Statement stmt : holder.statementTrace) {
JdbcUtils.close(stmt);
}
} finally {
holder.lock.unlock();
}
}
this.discardConnection(holder);
}
// holder.
LOG.error("{conn-" holder.getConnectionId() "} discard", error);
}handleFatalError方法这里会执行conn.disable(error)，然后标记requireDiscard为true，最后执行discardConnection
discardConnection
com/alibaba/druid/pool/DruidDataSource.java
代码语言：javascript复制 public void discardConnection(DruidConnectionHolder holder) {
if (holder == null) {
return;
}
Connection conn = holder.getConnection();
if (conn != null) {
JdbcUtils.close(conn);
}
lock.lock();
try {
if (holder.discard) {
return;
}
if (holder.active) {
activeCount--;
holder.active = false;
}
discardCount ;
holder.discard = true;
if (activeCount <= minIdle) {
emptySignal();
}
} finally {
lock.unlock();
}
}discardConnection这里会通过JdbcUtils.close(conn)关闭连接，然后加锁判断是否小于等于minIdle，若为true则执行emptySignal
小结
druid会在prepareStatement或者执行prepareStatement出现异常的时候执行conn.handleException，它委托给dataSource.handleConnectionException，后者会在exceptionSorter.isExceptionFatal(sqlEx)为true时会执行handleFatalError，handleFatalError方法这里会执行conn.disable(error)，然后标记requireDiscard为true，最后执行discardConnection来关闭连接。通过这样子来快速清理不可用的连接，避免连接池的连接不可用。
