Struts2的配置文件讀取(一)

struts2利用FilterDispatcher來攔截請求，然後進行請求的分發，在FilterDispatcher的#init()方法裏，實現了配置文件的讀入。

代碼如下：

Java代碼

public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig;
dispatcher = createDispatcher(filterConfig);
dispatcher.init();
String param = filterConfig.getInitParameter("packages");
String packages = "org.apache.struts2.static template org.apache.struts2.interceptor.debugging";
if (param != null) {
packages = param + " " + packages;
}
this.pathPrefixes = parse(packages);
}

    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
        
        dispatcher = createDispatcher(filterConfig);
        dispatcher.init();
        
        String param = filterConfig.getInitParameter("packages");
        String packages = "org.apache.struts2.static template org.apache.struts2.interceptor.debugging";
        if (param != null) {
            packages = param + " " + packages;
        }
        this.pathPrefixes = parse(packages);
    }

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先調用#createDispatcher()來創建一個Dispatcher對象，並將FilterConfig中的屬性讀出，代碼如下：

Java代碼

protected Dispatcher createDispatcher(FilterConfig filterConfig) {
Map params = new HashMap();
for (Enumeration e = filterConfig.getInitParameterNames(); e.hasMoreElements(); ) {
String name = (String) e.nextElement();
String value = filterConfig.getInitParameter(name);
params.put(name, value);
}
return new Dispatcher(filterConfig.getServletContext(), params);
}

    protected Dispatcher createDispatcher(FilterConfig filterConfig) {
        Map params = new HashMap();
        for (Enumeration e = filterConfig.getInitParameterNames(); e.hasMoreElements(); ) {
            String name = (String) e.nextElement();
            String value = filterConfig.getInitParameter(name);
            params.put(name, value);
        }
        return new Dispatcher(filterConfig.getServletContext(), params);
    }

在#createDispatcher()中，將Filter的配置中的所有屬性都寫入一個HashMap並作爲參數傳遞給Dispatcher的構造函數。

-------------------------------------------------------------------------------------------------

再回到#init()函數中，創建完Dispatcher對象後，緊接着調用Dispatcher的#init()方法。代碼如下：

Java代碼

public void init() {
if (configurationManager == null) {
configurationManager = new ConfigurationManager(BeanSelectionProvider.DEFAULT_BEAN_NAME);
}
init_DefaultProperties(); // [1]
init_TraditionalXmlConfigurations(); // [2]
init_LegacyStrutsProperties(); // [3]
init_ZeroConfiguration(); // [4]
init_CustomConfigurationProviders(); // [5]
init_MethodConfigurationProvider();
init_FilterInitParameters(); // [6]
init_AliasStandardObjects(); // [7]
Container container = init_PreloadConfiguration();
init_CheckConfigurationReloading(container);
init_CheckWebLogicWorkaround(container);
}

    public void init() {

        if (configurationManager == null) {
            configurationManager = new ConfigurationManager(BeanSelectionProvider.DEFAULT_BEAN_NAME);
        }

        init_DefaultProperties(); // [1]
        init_TraditionalXmlConfigurations(); // [2]
        init_LegacyStrutsProperties(); // [3]
        init_ZeroConfiguration(); // [4]
        init_CustomConfigurationProviders(); // [5]
        init_MethodConfigurationProvider();
        init_FilterInitParameters(); // [6]
        init_AliasStandardObjects(); // [7]

        Container container = init_PreloadConfiguration();
        init_CheckConfigurationReloading(container);
        init_CheckWebLogicWorkaround(container);

    }

首先實例化一個ConfigurationManager對象。

然後就是調用一系列的#init_*()方法了。

-------------------------------------------------------------------------------------------------

●第一個是

Java代碼

private void init_DefaultProperties() {
configurationManager.addConfigurationProvider(new DefaultPropertiesProvider());
}

    private void init_DefaultProperties() {
        configurationManager.addConfigurationProvider(new DefaultPropertiesProvider());
    }

這個方法中是將一個DefaultPropertiesProvider對象追加到ConfigurationManager對象內部的ConfigurationProvider隊列中。
DefaultPropertiesProvider的#register()方法可以載入org/apache/struts2/default.properties中定義的屬性。

-------------------------------------------------------------------------------------------------

●第二個是

Java代碼

private void init_TraditionalXmlConfigurations() {
String configPaths = initParams.get("config");
if (configPaths == null) {
configPaths = DEFAULT_CONFIGURATION_PATHS;
}
String[] files = configPaths.split("[url=file:////s*[,]//s]//s*[,]//s[/url]*");
for (String file : files) {
if (file.endsWith(".xml")) {
if ("xwork.xml".equals(file)) {
configurationManager.addConfigurationProvider(new XmlConfigurationProvider(
file, false));
} else {
configurationManager
.addConfigurationProvider(new StrutsXmlConfigurationProvider(file,
false, servletContext));
}
} else {
throw new IllegalArgumentException("Invalid configuration file name");
}
}
}

    private void init_TraditionalXmlConfigurations() {
        String configPaths = initParams.get("config");
        if (configPaths == null) {
            configPaths = DEFAULT_CONFIGURATION_PATHS;
        }
        String[] files = configPaths.split("[url=file:////s*[,]//s]//s*[,]//s[/url]*");
        for (String file : files) {
            if (file.endsWith(".xml")) {
                if ("xwork.xml".equals(file)) {
                    configurationManager.addConfigurationProvider(new XmlConfigurationProvider(
                            file, false));
                } else {
                    configurationManager
                            .addConfigurationProvider(new StrutsXmlConfigurationProvider(file,
                                    false, servletContext));
                }
            } else {
                throw new IllegalArgumentException("Invalid configuration file name");
            }
        }
    }

這裏負責載入的是FilterDispatcher的配置中所定義的config屬性。
如果用戶沒有定義config屬性，struts默認會載入DEFAULT_CONFIGURATION_PATHS這個值所代表的xml文件。
它的值爲"struts-default.xml,struts-plugin.xml,struts.xml"。也就是說框架默認會載入這三個項目xml文件。

下一步框架會逐個判斷每個config屬性中定義的文件。如果文件名爲"xwork.xml"，框架會用XmlConfigurationProvider類去處理，反之則用StrutsXmlConfigurationProvider類去處理。

-------------------------------------------------------------------------------------------------

●第三個是

Java代碼

private void init_LegacyStrutsProperties() {
configurationManager.addConfigurationProvider(new LegacyPropertiesConfigurationProvider());
}

    private void init_LegacyStrutsProperties() {
        configurationManager.addConfigurationProvider(new LegacyPropertiesConfigurationProvider());
    }

向ConfigurationManager加入了一個LegacyPropertiesConfigurationProvider。

-------------------------------------------------------------------------------------------------

●第四個是

Java代碼

private void init_ZeroConfiguration() {
String packages = initParams.get("actionPackages");
if (packages != null) {
String[] names = packages.split("[url=file:////s*[,]//s]//s*[,]//s[/url]*");
// Initialize the classloader scanner with the configured packages
if (names.length > 0) {
ClasspathConfigurationProvider provider = new ClasspathConfigurationProvider(names);
provider.setPageLocator(new ServletContextPageLocator(servletContext));
configurationManager.addConfigurationProvider(provider);
}
}
}

    private void init_ZeroConfiguration() {
        String packages = initParams.get("actionPackages");
        if (packages != null) {
            String[] names = packages.split("[url=file:////s*[,]//s]//s*[,]//s[/url]*");
            // Initialize the classloader scanner with the configured packages
            if (names.length > 0) {
                ClasspathConfigurationProvider provider = new ClasspathConfigurationProvider(names);
                provider.setPageLocator(new ServletContextPageLocator(servletContext));
                configurationManager.addConfigurationProvider(provider);
            }
        }
    }

這次處理的是FilterDispatcher的配置中所定義的actionPackages屬性。傳說中的Struts 2 零配置。
該參數的值是一個以英文逗號(,)隔開的字符串，每個字符串都是一個包空間，Struts 2框架將掃描這些包空間下的Action類。

-------------------------------------------------------------------------------------------------

●第五個是

Java代碼

private void init_CustomConfigurationProviders() {
String configProvs = initParams.get("configProviders");
if (configProvs != null) {
String[] classes = configProvs.split("[url=file:////s*[,]//s]//s*[,]//s[/url]*");
for (String cname : classes) {
try {
Class cls = ClassLoaderUtils.loadClass(cname, this.getClass());
ConfigurationProvider prov = (ConfigurationProvider) cls.newInstance();
configurationManager.addConfigurationProvider(prov);
} catch (InstantiationException e) {
throw new ConfigurationException("Unable to instantiate provider: " + cname, e);
} catch (IllegalAccessException e) {
throw new ConfigurationException("Unable to access provider: " + cname, e);
} catch (ClassNotFoundException e) {
throw new ConfigurationException("Unable to locate provider class: " + cname, e);
}
}
}
}

    private void init_CustomConfigurationProviders() {
        String configProvs = initParams.get("configProviders");
        if (configProvs != null) {
            String[] classes = configProvs.split("[url=file:////s*[,]//s]//s*[,]//s[/url]*");
            for (String cname : classes) {
                try {
                    Class cls = ClassLoaderUtils.loadClass(cname, this.getClass());
                    ConfigurationProvider prov = (ConfigurationProvider) cls.newInstance();
                    configurationManager.addConfigurationProvider(prov);
                } catch (InstantiationException e) {
                    throw new ConfigurationException("Unable to instantiate provider: " + cname, e);
                } catch (IllegalAccessException e) {
                    throw new ConfigurationException("Unable to access provider: " + cname, e);
                } catch (ClassNotFoundException e) {
                    throw new ConfigurationException("Unable to locate provider class: " + cname, e);
                }
            }
        }
    }

此方法處理的是FilterDispatcher的配置中所定義的configProviders屬性。負責載入用戶自定義的ConfigurationProvider。

-------------------------------------------------------------------------------------------------

●第六個是

Java代碼

private void init_FilterInitParameters() {
configurationManager.addConfigurationProvider(new ConfigurationProvider() {
public void destroy() {
}
public void init(Configuration configuration) throws ConfigurationException {
}
public void loadPackages() throws ConfigurationException {
}
public boolean needsReload() {
return false;
}
public void register(ContainerBuilder builder, LocatableProperties props)
throws ConfigurationException {
props.putAll(initParams);
}
});
}

    private void init_FilterInitParameters() {
        configurationManager.addConfigurationProvider(new ConfigurationProvider() {
            public void destroy() {
            }

            public void init(Configuration configuration) throws ConfigurationException {
            }

            public void loadPackages() throws ConfigurationException {
            }

            public boolean needsReload() {
                return false;
            }

            public void register(ContainerBuilder builder, LocatableProperties props)
                    throws ConfigurationException {
                props.putAll(initParams);
            }
        });
    }

此方法用來處理FilterDispatcher的配置中所定義的所有屬性。

-------------------------------------------------------------------------------------------------

●第七個是

Java代碼

private void init_AliasStandardObjects() {
configurationManager.addConfigurationProvider(new BeanSelectionProvider());
}

	private void init_AliasStandardObjects() {
		configurationManager.addConfigurationProvider(new BeanSelectionProvider());
	}

-------------------------------------------------------------------------------------------------

執行完七個init_*方法後，Dispatcher的#init()會接着調用#init_PreloadConfiguration()，構建一個用於依賴注射的Container對象。

Java代碼

private Container init_PreloadConfiguration() {
Configuration config = configurationManager.getConfiguration();
Container container = config.getContainer();
boolean reloadi18n = Boolean.valueOf(container.getInstance(String.class,
StrutsConstants.STRUTS_I18N_RELOAD));
LocalizedTextUtil.setReloadBundles(reloadi18n);
ObjectTypeDeterminer objectTypeDeterminer = container
.getInstance(ObjectTypeDeterminer.class);
ObjectTypeDeterminerFactory.setInstance(objectTypeDeterminer);
return container;
}

    private Container init_PreloadConfiguration() {
        Configuration config = configurationManager.getConfiguration();
        Container container = config.getContainer();

        boolean reloadi18n = Boolean.valueOf(container.getInstance(String.class,
                StrutsConstants.STRUTS_I18N_RELOAD));
        LocalizedTextUtil.setReloadBundles(reloadi18n);

        ObjectTypeDeterminer objectTypeDeterminer = container
                .getInstance(ObjectTypeDeterminer.class);
        ObjectTypeDeterminerFactory.setInstance(objectTypeDeterminer);

        return container;
    }

此方法首先獲取到ConfigurationManager中的Configuration對象，在#getConfiguration()內部，調用上邊6步添加到ConfigurationManager的ConfigurationProviders的#register()方法。

Java代碼

public synchronized Configuration getConfiguration() {
if (configuration == null) {
setConfiguration(new DefaultConfiguration(defaultFrameworkBeanName));
try {
configuration.reload(getConfigurationProviders());
} catch (ConfigurationException e) {
setConfiguration(null);
throw e;
}
} else {
conditionalReload();
}
return configuration;
}

    public synchronized Configuration getConfiguration() {
        if (configuration == null) {
            setConfiguration(new DefaultConfiguration(defaultFrameworkBeanName));
            try {
              configuration.reload(getConfigurationProviders());
            } catch (ConfigurationException e) {
              setConfiguration(null);
              throw e;
            }
        } else {
            conditionalReload();
        }

        return configuration;
    }

其中的重點就是DefaultConfiguration的#reload()方法。

Java代碼

public synchronized void reload(List providers) throws ConfigurationException {
packageContexts.clear();
loadedFileNames.clear();
ContainerProperties props = new ContainerProperties();
ContainerBuilder builder = new ContainerBuilder();
for (ConfigurationProvider configurationProvider : providers)
{
configurationProvider.init(this);
configurationProvider.register(builder, props);
}
props.setConstants(builder);
builder.factory(Configuration.class, new Factory() {
public Configuration create(Context context) throws Exception {
return DefaultConfiguration.this;
}
});
try {
// Set the object factory for the purposes of factory creation
ObjectFactory.setObjectFactory(new ObjectFactory());
container = builder.create(false);
objectFactory = container.getInstance(ObjectFactory.class);
ObjectFactory.setObjectFactory(objectFactory);
for (ConfigurationProvider configurationProvider : providers)
{
container.inject(configurationProvider);
configurationProvider.loadPackages();
}
rebuildRuntimeConfiguration();
} finally {
ObjectFactory.setObjectFactory(null);
}
}

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