netty检测系统工具PlatformDependent

1. 检测jdk版本

 @SuppressWarnings("LoopStatementThatDoesntLoop")
    private static int javaVersion0() {
        int javaVersion;

        // Not really a loop
        for (;;) {
            // Android
            if (isAndroid()) {
                javaVersion = 6;
                break;
            }

            try {
                Class.forName("java.time.Clock", false, getClassLoader(Object.class));
                javaVersion = 8;
                break;
            } catch (Exception e) {
                // Ignore
            }

            try {
                Class.forName("java.util.concurrent.LinkedTransferQueue", false, getClassLoader(BlockingQueue.class));
                javaVersion = 7;
                break;
            } catch (Exception e) {
                // Ignore
            }

            javaVersion = 6;
            break;
        }

        if (logger.isDebugEnabled()) {
            logger.debug("Java version: {}", javaVersion);
        }
        return javaVersion;
    }

2. 检测是否window

    private static boolean isWindows0() {
        boolean windows = SystemPropertyUtil.get("os.name", "").toLowerCase(Locale.US).contains("win");
        if (windows) {
            logger.debug("Platform: Windows");
        }
        return windows;
    }

3. 检测是否root权限

private static boolean isRoot0() {
        if (isWindows()) {
            return false;
        }

        String[] ID_COMMANDS = { "/usr/bin/id", "/bin/id", "/usr/xpg4/bin/id", "id"};
        Pattern UID_PATTERN = Pattern.compile("^(?:0|[1-9][0-9]*)$");
        for (String idCmd: ID_COMMANDS) {
            Process p = null;
            BufferedReader in = null;
            String uid = null;
            try {
                p = Runtime.getRuntime().exec(new String[] { idCmd, "-u" });
                in = new BufferedReader(new InputStreamReader(p.getInputStream(), CharsetUtil.US_ASCII));
                uid = in.readLine();
                in.close();

                for (;;) {
                    try {
                        int exitCode = p.waitFor();
                        if (exitCode != 0) {
                            uid = null;
                        }
                        break;
                    } catch (InterruptedException e) {
                        // Ignore
                    }
                }
            } catch (Exception e) {
                // Failed to run the command.
                uid = null;
            } finally {
                if (in != null) {
                    try {
                        in.close();
                    } catch (IOException e) {
                        // Ignore
                    }
                }
                if (p != null) {
                    try {
                        p.destroy();
                    } catch (Exception e) {
                        // Android sometimes triggers an ErrnoException.
                    }
                }
            }

            if (uid != null && UID_PATTERN.matcher(uid).matches()) {
                logger.debug("UID: {}", uid);
                return "0".equals(uid);
            }
        }

        logger.debug("Could not determine the current UID using /usr/bin/id; attempting to bind at privileged ports.");

        Pattern PERMISSION_DENIED = Pattern.compile(".*(?:denied|not.*permitted).*");
        for (int i = 1023; i > 0; i --) {
            ServerSocket ss = null;
            try {
                ss = new ServerSocket();
                ss.setReuseAddress(true);
                ss.bind(new InetSocketAddress(i));
                if (logger.isDebugEnabled()) {
                    logger.debug("UID: 0 (succeded to bind at port {})", i);
                }
                return true;
            } catch (Exception e) {
                // Failed to bind.
                // Check the error message so that we don't always need to bind 1023 times.
                String message = e.getMessage();
                if (message == null) {
                    message = "";
                }
                message = message.toLowerCase();
                if (PERMISSION_DENIED.matcher(message).matches()) {
                    break;
                }
            } finally {
                if (ss != null) {
                    try {
                        ss.close();
                    } catch (Exception e) {
                        // Ignore.
                    }
                }
            }
        }

        logger.debug("UID: non-root (failed to bind at any privileged ports)");
        return false;
    }

4.检测最大直接内存

private static long maxDirectMemory0() {
        long maxDirectMemory = 0;
        try {
            // Try to get from sun.misc.VM.maxDirectMemory() which should be most accurate.
            Class<?> vmClass = Class.forName("sun.misc.VM", true, getSystemClassLoader());
            Method m = vmClass.getDeclaredMethod("maxDirectMemory");
            maxDirectMemory = ((Number) m.invoke(null)).longValue();
        } catch (Throwable t) {
            // Ignore
        }

        if (maxDirectMemory > 0) {
            return maxDirectMemory;
        }

        try {
            // Now try to get the JVM option (-XX:MaxDirectMemorySize) and parse it.
            // Note that we are using reflection because Android doesn't have these classes.
            Class<?> mgmtFactoryClass = Class.forName(
                    "java.lang.management.ManagementFactory", true, getSystemClassLoader());
            Class<?> runtimeClass = Class.forName(
                    "java.lang.management.RuntimeMXBean", true, getSystemClassLoader());

            Object runtime = mgmtFactoryClass.getDeclaredMethod("getRuntimeMXBean").invoke(null);

            @SuppressWarnings("unchecked")
            List<String> vmArgs = (List<String>) runtimeClass.getDeclaredMethod("getInputArguments").invoke(runtime);
            for (int i = vmArgs.size() - 1; i >= 0; i --) {
                Matcher m = MAX_DIRECT_MEMORY_SIZE_ARG_PATTERN.matcher(vmArgs.get(i));
                if (!m.matches()) {
                    continue;
                }

                maxDirectMemory = Long.parseLong(m.group(1));
                switch (m.group(2).charAt(0)) {
                    case 'k': case 'K':
                        maxDirectMemory *= 1024;
                        break;
                    case 'm': case 'M':
                        maxDirectMemory *= 1024 * 1024;
                        break;
                    case 'g': case 'G':
                        maxDirectMemory *= 1024 * 1024 * 1024;
                        break;
                }
                break;
            }
        } catch (Throwable t) {
            // Ignore
        }

        if (maxDirectMemory <= 0) {
            maxDirectMemory = Runtime.getRuntime().maxMemory();
            logger.debug("maxDirectMemory: {} bytes (maybe)", maxDirectMemory);
        } else {
            logger.debug("maxDirectMemory: {} bytes", maxDirectMemory);
        }

        return maxDirectMemory;
    }

等等