tomcat jdbc pool的borrow和return

borrow

tomcat-jdbc-8.5.11-sources.jar!/org/apache/tomcat/jdbc/pool/ConnectionPool.java

/**
     * Validates and configures a previously idle connection
     * @param now - timestamp
     * @param con - the connection to validate and configure
     * @param username The user name to use for the connection
     * @param password The password for the connection
     * @return a connection
     * @throws SQLException if a validation error happens
     */
    protected PooledConnection borrowConnection(long now, PooledConnection con, String username, String password) throws SQLException {
        //we have a connection, lets set it up

        //flag to see if we need to nullify
        boolean setToNull = false;
        try {
            con.lock();
            if (con.isReleased()) {
                return null;
            }

            //evaluate username/password change as well as max age functionality
            boolean forceReconnect = con.shouldForceReconnect(username, password) || con.isMaxAgeExpired();

            if (!con.isDiscarded() && !con.isInitialized()) {
                //here it states that the connection not discarded, but the connection is null
                //don't attempt a connect here. It will be done during the reconnect.
                forceReconnect = true;
            }

            if (!forceReconnect) {
                if ((!con.isDiscarded()) && con.validate(PooledConnection.VALIDATE_BORROW)) {
                    //set the timestamp
                    con.setTimestamp(now);
                    if (getPoolProperties().isLogAbandoned()) {
                        //set the stack trace for this pool
                        con.setStackTrace(getThreadDump());
                    }
                    if (!busy.offer(con)) {
                        log.debug("Connection doesn't fit into busy array, connection will not be traceable.");
                    }
                    return con;
                }
            }
            //if we reached here, that means the connection
            //is either has another principal, is discarded or validation failed.
            //we will make one more attempt
            //in order to guarantee that the thread that just acquired
            //the connection shouldn't have to poll again.
            try {
                con.reconnect();
                reconnectedCount.incrementAndGet();
                int validationMode = getPoolProperties().isTestOnConnect() || getPoolProperties().getInitSQL()!=null ?
                    PooledConnection.VALIDATE_INIT :
                    PooledConnection.VALIDATE_BORROW;

                if (con.validate(validationMode)) {
                    //set the timestamp
                    con.setTimestamp(now);
                    if (getPoolProperties().isLogAbandoned()) {
                        //set the stack trace for this pool
                        con.setStackTrace(getThreadDump());
                    }
                    if (!busy.offer(con)) {
                        log.debug("Connection doesn't fit into busy array, connection will not be traceable.");
                    }
                    return con;
                } else {
                    //validation failed.
                    throw new SQLException("Failed to validate a newly established connection.");
                }
            } catch (Exception x) {
                release(con);
                setToNull = true;
                if (x instanceof SQLException) {
                    throw (SQLException)x;
                } else {
                    SQLException ex  = new SQLException(x.getMessage());
                    ex.initCause(x);
                    throw ex;
                }
            }
        } finally {
            con.unlock();
            if (setToNull) {
                con = null;
            }
        }
    }

return

tomcat-jdbc-8.5.11-sources.jar!/org/apache/tomcat/jdbc/pool/ConnectionPool.java

/**
     * Returns a connection to the pool
     * If the pool is closed, the connection will be released
     * If the connection is not part of the busy queue, it will be released.
     * If {@link PoolProperties#testOnReturn} is set to true it will be validated
     * @param con PooledConnection to be returned to the pool
     */
    protected void returnConnection(PooledConnection con) {
        if (isClosed()) {
            //if the connection pool is closed
            //close the connection instead of returning it
            release(con);
            return;
        } //end if

        if (con != null) {
            try {
                returnedCount.incrementAndGet();
                con.lock();
                if (con.isSuspect()) {
                    if (poolProperties.isLogAbandoned() && log.isInfoEnabled()) {
                        log.info("Connection(" + con + ") that has been marked suspect was returned."
                                + " The processing time is " + (System.currentTimeMillis()-con.getTimestamp()) + " ms.");
                    }
                    if (jmxPool!=null) {
                        jmxPool.notify(org.apache.tomcat.jdbc.pool.jmx.ConnectionPool.SUSPECT_RETURNED_NOTIFICATION,
                                "Connection(" + con + ") that has been marked suspect was returned.");
                    }
                }
                if (busy.remove(con)) {

                    if (!shouldClose(con,PooledConnection.VALIDATE_RETURN)) {
                        con.setStackTrace(null);
                        con.setTimestamp(System.currentTimeMillis());
                        if (((idle.size()>=poolProperties.getMaxIdle()) && !poolProperties.isPoolSweeperEnabled()) || (!idle.offer(con))) {
                            if (log.isDebugEnabled()) {
                                log.debug("Connection ["+con+"] will be closed and not returned to the pool, idle["+idle.size()+"]>=maxIdle["+poolProperties.getMaxIdle()+"] idle.offer failed.");
                            }
                            release(con);
                        }
                    } else {
                        if (log.isDebugEnabled()) {
                            log.debug("Connection ["+con+"] will be closed and not returned to the pool.");
                        }
                        release(con);
                    } //end if
                } else {
                    if (log.isDebugEnabled()) {
                        log.debug("Connection ["+con+"] will be closed and not returned to the pool, busy.remove failed.");
                    }
                    release(con);
                }
            } finally {
                con.unlock();
            }
        } //end if
    } //checkIn

validation

/**
     * Returns <code>true</code> if the connection pool is configured
     * to do validation for a certain action.
     * @param action The validation action
     */
    private boolean doValidate(int action) {
        if (action == PooledConnection.VALIDATE_BORROW &&
            poolProperties.isTestOnBorrow())
            return true;
        else if (action == PooledConnection.VALIDATE_RETURN &&
                 poolProperties.isTestOnReturn())
            return true;
        else if (action == PooledConnection.VALIDATE_IDLE &&
                 poolProperties.isTestWhileIdle())
            return true;
        else if (action == PooledConnection.VALIDATE_INIT &&
                 poolProperties.isTestOnConnect())
            return true;
        else if (action == PooledConnection.VALIDATE_INIT &&
                 poolProperties.getInitSQL()!=null)
           return true;
        else
            return false;
    }

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