Latke 代码阅读－1 Latke.java

大致的代码结构：

• java
• b3log
  • cache,cron,event,image,intercept,ioc
  • logging,mail,model,plugin,remote,repository
  • service,servlet,taskqueue,thread,urlfetch,user,util
  • Latkes.java
  • Keys.java,Runtimetabase.java,RuntimeEnv.java,RuntimeMode.java
• json
• weborganic
• resources
  • beans.xml

Latkes.java 下面那一行涉及的代码基本没有逻辑，全是枚举或者常量值的定义，想来无可研究。
开始的字段定义继续忽略，首先是静态代码块（删去了 LOGGER）：

static {
        try {
            final InputStream resourceAsStream = Latkes.class.getResourceAsStream("/latke.properties");
            if (null != resourceAsStream) {
                LATKE_PROPS.load(resourceAsStream);
            }
        } catch (final Exception e) {
            throw new RuntimeException("Not found latke.properties");
        }
        try {
            final InputStream resourceAsStream = Latkes.class.getResourceAsStream("/local.properties");
            if (null != resourceAsStream) {
                LOCAL_PROPS.load(resourceAsStream);
            }
        } catch (final Exception e) {
        }
        try {
            final InputStream resourceAsStream = Latkes.class.getResourceAsStream("/remote.properties");
            if (null != resourceAsStream) {
                REMOTE_PROPS.load(resourceAsStream);
            }
        } catch (final Exception e) {
        }
    }

需要注意的点：

• 静态代码块，意味着这段代码将在类实例化的时候首先得到执行
• Latkes.class.getResourceAsStream，这个用法不知是什么
• LATKE_PROPS 是 Properties 类型

接下来大部分是从 properties 文件里获取配置的方法，不一一列举，如：

public static String getStaticResourceVersion() {
        //如果没有值，则从配置文件中读取，否则直接返回
        if (null == staticResourceVersion) {
            staticResourceVersion = LATKE_PROPS.getProperty("staticResourceVersion");
            //如果没有读取到，则赋予默认值
            if (null == staticResourceVersion) {
                staticResourceVersion = startupTimeMillis;
            }
        }
        return staticResourceVersion;
    }

初始化运行环境，Starter 类会调用该方法：

public static void initRuntimeEnv() {
        if (null != runtimeEnv) {
            return;
        }
        final String runtimeEnvValue = LATKE_PROPS.getProperty("runtimeEnv"); //latke.properties
        if (null != runtimeEnvValue) {
            //如果不为空,说明配置里有设置,读取设置
            runtimeEnv = RuntimeEnv.valueOf(runtimeEnvValue);
        }
        //配置为空,设置为-本地
        runtimeEnv = RuntimeEnv.LOCAL;
        //获取设置运行模式
        if (null == runtimeMode) {
            final String runtimeModeValue = LATKE_PROPS.getProperty("runtimeMode");
            if (null != runtimeModeValue) {
                runtimeMode = RuntimeMode.valueOf(runtimeModeValue);
            } else {
                runtimeMode = RuntimeMode.PRODUCTION;
            }
        }
        if (RuntimeEnv.LOCAL == runtimeEnv) {
            // Read local database configurations
            final RuntimeDatabase runtimeDatabase = getRuntimeDatabase();
            //local.properties
            if (RuntimeDatabase.H2 == runtimeDatabase) {
                final String newTCPServer = Latkes.getLocalProperty("newTCPServer");
                if ("true".equals(newTCPServer)) {
                    final String jdbcURL = Latkes.getLocalProperty("jdbc.URL");
                    if (Strings.isEmptyOrNull(jdbcURL)) {
                        throw new IllegalStateException("The jdbc.URL in local.properties is required");
                    }
                    final String[] parts = jdbcURL.split(":");
                    if (parts.length != Integer.valueOf("5")/* CheckStyle.... */) {
                        throw new IllegalStateException("jdbc.URL should like [jdbc:h2:tcp://localhost:8250/~/] (the port part is required)");
                    }
                    String port = parts[parts.length - 1];
                    port = StringUtils.substringBefore(port, "/");
                    try {
                        h2 = org.h2.tools.Server.createTcpServer(new String[]{"-tcpPort", port, "-tcpAllowOthers"}).start();
                    } catch (final SQLException e) {
                        final String msg = "H2 TCP server create failed";
                        throw new IllegalStateException(msg);
                    }
                }
            }
        }
        locale = new Locale("en_US");
    }

• 这段代码中包含了当数据库是 H2 时的处理，大概时使用该数据库时要自己做的事情吧，毕竟是纯 Java 库，想来不必深究，其文档应该有说明。
• Locale 类的作用意义不明。

关闭 Latke

public static void shutdown() {
        try {
            if (RuntimeEnv.LOCAL != getRuntimeEnv()) {
                return;
            }
            //关闭数据库连接池
            Connections.shutdownConnectionPool();
            final RuntimeDatabase runtimeDatabase = getRuntimeDatabase();
            switch (runtimeDatabase) {
                case H2:
                    final String newTCPServer = Latkes.getLocalProperty("newTCPServer");
                    if ("true".equals(newTCPServer)) {
                        h2.stop();
                        h2.shutdown();
                    }
                    break;
                default:
            }
            //关闭定时任务
            CronService.shutdown();
           //关闭执行的线程
            LocalThreadService.EXECUTOR_SERVICE.shutdown();
        } catch (final Exception e) {
        }
        //停止应用生命周期
        Lifecycle.endApplication();
        // This manually deregisters JDBC driver, which prevents Tomcat from complaining about memory leaks
        //注销数据库连接驱动
        final Enumeration<Driver> drivers = DriverManager.getDrivers();
        while (drivers.hasMoreElements()) {
            final Driver driver = drivers.nextElement();
            try {
                DriverManager.deregisterDriver(driver);
            } catch (final SQLException e) {
            }
        }
    }

• Connections, CronService, LocalThreadService, Lifecycle 均为 b3log 包下的类，此时暂不做进一步研究。
• Driver 为 java.sql 包下的类。

加载皮肤，这个看似跟 MVC 无关的内容，放在这里，有点琢磨不透，可能是因为预先想到了由不同的皮肤，而在公共的框架上提供了支持吧：

public static void loadSkin(final String skinDirName) {
        final ServletContext servletContext = AbstractServletListener.getServletContext();
        Templates.MAIN_CFG.setServletContextForTemplateLoading(servletContext, "skins/" + skinDirName);
        Latkes.setTimeZone("Asia/Shanghai");
}

• AbstractServletListener, Templates 为 b3log 的类，暂不详查
• ServletContext 有什么特殊的地方？

获取皮肤名称：

public static String getSkinName(final String skinDirName) {
        try {
            final Properties ret = new Properties();
            final File file = getWebFile("/skins/" + skinDirName + "/skin.properties");
            ret.load(new FileInputStream(file));
            return ret.getProperty("name");
        } catch (final Exception e) {
            return null;
        }
    }
public static File getWebFile(final String path) {
        final ServletContext servletContext = AbstractServletListener.getServletContext();
        File ret;
        try {
            final URL resource = servletContext.getResource(path);
            if (null == resource) {
                return null;
            }
            ret = FileUtils.toFile(resource);
            if (null == ret) {
                final File tempdir = (File) servletContext.getAttribute("javax.servlet.context.tempdir");
                ret = new File(tempdir.getPath() + path);
                FileUtils.copyURLToFile(resource, ret);
                ret.deleteOnExit();
            }
            return ret;
        } catch (final Exception e) {
            return null;
        }
    }