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Diffstat (limited to 'examples_java/src/db/LockExample.java')
| -rw-r--r-- | examples_java/src/db/LockExample.java | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/examples_java/src/db/LockExample.java b/examples_java/src/db/LockExample.java new file mode 100644 index 0000000..7b20838 --- /dev/null +++ b/examples_java/src/db/LockExample.java @@ -0,0 +1,226 @@ +/*- + * See the file LICENSE for redistribution information. + * + * Copyright (c) 1997-2009 Oracle. All rights reserved. + * + * $Id$ + */ + +package db; + +import com.sleepycat.db.*; +import java.io.File; +import java.io.FileNotFoundException; +import java.io.InputStreamReader; +import java.io.IOException; +import java.io.PrintStream; +import java.util.Vector; + +// +// An example of a program using Lock and related classes. +// +class LockExample { + private static final String progname = "LockExample"; + private static final File LOCK_HOME = new File("TESTDIR"); + Environment dbenv; + + public LockExample(File home, int maxlocks, boolean do_unlink) + throws DatabaseException, FileNotFoundException { + + if (do_unlink) { + Environment.remove(home, true, null); + } + + EnvironmentConfig config = new EnvironmentConfig(); + config.setErrorStream(System.err); + config.setErrorPrefix("LockExample"); + config.setMaxLocks(maxlocks); + config.setAllowCreate(true); + config.setInitializeLocking(true); + dbenv = new Environment(home, config); + } + + public void close() throws DatabaseException { + dbenv.close(); + } + + // Prompts for a line, returning the default answer if a blank + // line is entered. + // + public static String askForLine(InputStreamReader reader, + PrintStream out, String prompt, + String defaultAnswer) { + String result; + do { + if (defaultAnswer != null) + out.print(prompt + " [" + defaultAnswer + "] >"); + else + out.print(prompt); + out.flush(); + result = getLine(reader); + if (result == null || result.length() == 0) + result = defaultAnswer; + } while (result == null); + return result; + } + + // Not terribly efficient, but does the job. + // Works for reading a line from stdin or a file. + // Returns null on EOF. If EOF appears in the middle + // of a line, returns that line, then null on next call. + // + public static String getLine(InputStreamReader reader) { + StringBuffer b = new StringBuffer(); + int c; + try { + while ((c = reader.read()) != -1 && c != '\n') + if (c != '\r') + b.append((char)c); + } catch (IOException ioe) { + c = -1; + } + + if (c == -1 && b.length() == 0) + return null; + else + return b.toString(); + } + + public void run() throws DatabaseException { + long held; + int len = 0, locker; + int ret; + boolean did_get = false; + int lockid = 0; + InputStreamReader in = new InputStreamReader(System.in); + Vector locks = new Vector(); + + // + // Accept lock requests. + // + locker = dbenv.createLockerID(); + for (held = 0;;) { + String opbuf = askForLine(in, System.out, + "Operation get/release", "get"); + if (opbuf == null) + break; + + try { + if (opbuf.equals("get") || opbuf.equals("vget")) { + // Acquire a lock. + String objbuf = askForLine(in, System.out, + "input object (text string) to lock> ", null); + if (objbuf == null) + break; + + String lockbuf; + do { + lockbuf = askForLine(in, System.out, + "lock type read/write", "read"); + if (lockbuf == null) + break; + len = lockbuf.length(); + } while (len >= 1 && + !lockbuf.equals("read") && + !lockbuf.equals("write")); + + LockRequestMode lock_type; + if (len <= 1 || lockbuf.equals("read")) + lock_type = LockRequestMode.READ; + else + lock_type = LockRequestMode.WRITE; + + DatabaseEntry entry = new DatabaseEntry(objbuf.getBytes()); + + Lock lock; + if (opbuf.equals("get")) { + did_get = true; + lock = dbenv.getLock(locker, true, entry, lock_type); + } else { + LockRequest req = new LockRequest( + LockOperation.GET, lock_type, entry, null); + LockRequest[] reqs = { req }; + dbenv.lockVector(locker, true, reqs); + lock = req.getLock(); + System.out.println("Got lock: " + lock); + } + lockid = locks.size(); + locks.addElement(lock); + } else { + // Release a lock. + String objbuf; + objbuf = askForLine(in, System.out, + "input lock to release> ", null); + if (objbuf == null) + break; + + lockid = Integer.parseInt(objbuf, 16); + if (lockid < 0 || lockid >= locks.size()) { + System.out.println("Lock #" + lockid + " out of range"); + continue; + } + did_get = false; + Lock lock = (Lock)locks.elementAt(lockid); + dbenv.putLock(lock); + } + System.out.println("Lock #" + lockid + " " + + (did_get ? "granted" : "released")); + held += did_get ? 1 : -1; + } catch (LockNotGrantedException lnge) { + System.err.println("Lock not granted"); + } catch (DeadlockException de) { + System.err.println("LockExample: lock_" + + (did_get ? "get" : "put") + + ": returned DEADLOCK"); + } catch (DatabaseException dbe) { + System.err.println("LockExample: lock_get: " + dbe.toString()); + } + } + System.out.println(); + System.out.println("Closing lock region " + String.valueOf(held) + + " locks held"); + } + + private static void usage() { + System.err.println("usage: LockExample [-u] [-h home] [-m maxlocks]"); + System.exit(1); + } + + public static void main(String[] argv) { + File home = LOCK_HOME; + boolean do_unlink = false; + int maxlocks = 0; + + for (int i = 0; i < argv.length; ++i) { + if (argv[i].equals("-h")) { + if (++i >= argv.length) + usage(); + home = new File(argv[i]); + } else if (argv[i].equals("-m")) { + if (++i >= argv.length) + usage(); + + try { + maxlocks = Integer.parseInt(argv[i]); + } catch (NumberFormatException nfe) { + usage(); + } + } else if (argv[i].equals("-u")) { + do_unlink = true; + } else { + usage(); + } + } + + try { + LockExample app = new LockExample(home, maxlocks, do_unlink); + app.run(); + app.close(); + } catch (DatabaseException dbe) { + System.err.println(progname + ": " + dbe.toString()); + } catch (Throwable t) { + System.err.println(progname + ": " + t.toString()); + } + System.out.println("LockExample completed"); + } +} |