初始化方法学习
public class ActionServlet extends HttpServlet
//servlet初始化
public void init() throws ServletException {
final String configPrefix = "config/";
final int configPrefixLength = configPrefix.length() - 1;
// Wraps the entire initialization in a try/catch to better handle
// unexpected exceptions and errors to provide better feedback
// to the developer
try {
initInternal();
initOther();
initServlet();
initChain();
getServletContext().setAttribute(Globals.ACTION_SERVLET_KEY, this);
initModuleConfigFactory();
// Initialize modules as needed
ModuleConfig moduleConfig = initModuleConfig("", config);
initModuleMessageResources(moduleConfig);
initModulePlugIns(moduleConfig);
initModuleFormBeans(moduleConfig);
initModuleForwards(moduleConfig);
initModuleExceptionConfigs(moduleConfig);
initModuleActions(moduleConfig);
moduleConfig.freeze();
Enumeration names = getServletConfig().getInitParameterNames();
while (names.hasMoreElements()) {
String name = (String) names.nextElement();
if (!name.startsWith(configPrefix)) {
continue;
}
String prefix = name.substring(configPrefixLength);
moduleConfig =
initModuleConfig(prefix,
getServletConfig().getInitParameter(name));
initModuleMessageResources(moduleConfig);
initModulePlugIns(moduleConfig);
initModuleFormBeans(moduleConfig);
initModuleForwards(moduleConfig);
initModuleExceptionConfigs(moduleConfig);
initModuleActions(moduleConfig);
moduleConfig.freeze();
}
this.initModulePrefixes(this.getServletContext());
this.destroyConfigDigester();
} catch (UnavailableException ex) {
throw ex;
} catch (Throwable t) {
// The follow error message is not retrieved from internal message
// resources as they may not have been able to have been
// initialized
log.error("Unable to initialize Struts ActionServlet due to an "
+ "unexpected exception or error thrown, so marking the "
+ "servlet as unavailable. Most likely, this is due to an "
+ "incorrect or missing library dependency.", t);
throw new UnavailableException(t.getMessage());
}
}1、initInternal方法
protected void initInternal()
throws ServletException {
try {
//internalName是org.apache.struts.action.ActionResources
internal = MessageResources.getMessageResources(internalName);
} catch (MissingResourceException e) {
log.error("Cannot load internal resources from '" + internalName
+ "'", e);
throw new UnavailableException(
"Cannot load internal resources from '" + internalName + "'");
}
}看一下org.apache.struts.action.ActionResources，提示信息数据，我这看到的是英文版和日文版
该方法主要就是加载提示信息数据，加载完成后保存到internal这个属性里
2、initOther方法
protected void initOther()
throws ServletException {
String value;
//读取actionservlet的配置文件，config默认是/WEB-INF/struts-config.xml
value = getServletConfig().getInitParameter("config");
if (value != null) {
config = value;
}
// Backwards compatibility for form beans of Java wrapper classes
// Set to true for strict Struts 1.0 compatibility
//从web.xml读取数据转换器开关
value = getServletConfig().getInitParameter("convertNull");
if ("true".equalsIgnoreCase(value) || "yes".equalsIgnoreCase(value)
|| "on".equalsIgnoreCase(value) || "y".equalsIgnoreCase(value)
|| "1".equalsIgnoreCase(value)) {
convertNull = true;
}
if (convertNull) {
ConvertUtils.deregister();
//几种类型转换
ConvertUtils.register(new BigDecimalConverter(null),
BigDecimal.class);
ConvertUtils.register(new BigIntegerConverter(null),
BigInteger.class);
ConvertUtils.register(new BooleanConverter(null), Boolean.class);
ConvertUtils.register(new ByteConverter(null), Byte.class);
ConvertUtils.register(new CharacterConverter(null), Character.class);
ConvertUtils.register(new DoubleConverter(null), Double.class);
ConvertUtils.register(new FloatConverter(null), Float.class);
ConvertUtils.register(new IntegerConverter(null), Integer.class);
ConvertUtils.register(new LongConverter(null), Long.class);
ConvertUtils.register(new ShortConverter(null), Short.class);
}
}3、initServlet（）方法
读取并解析struts的配置文件（struts-config.xml）
protected void initServlet()
throws ServletException {
// Remember our servlet name
//通过servletconfig获得该servlet名称
this.servletName = getServletConfig().getServletName();
// Prepare a Digester to scan the web application deployment descriptor
//apache的一个xml解析工具
Digester digester = new Digester();
//把当前对象（ActinServlet）放入digester中
digester.push(this);
digester.setNamespaceAware(true);
digester.setValidating(false);
// Register our local copy of the DTDs that we can find
//解析了几个dtd，struts1自带的
for (int i = 0; i < registrations.length; i += 2) {
URL url = this.getClass().getResource(registrations[i + 1]);
if (url != null) {
digester.register(registrations[i], url.toString());
}
}
// Configure the processing rules that we need
//类似xpath，得到web-app/servlet-mapping下的参数，并传给ActinServletaddServletMapping方法执行</span>
digester.addCallMethod("web-app/servlet-mapping", "addServletMapping", 2);
//将web-app/servlet-mapping/servlet-name的值，作为方法的第一个参数
digester.addCallParam("web-app/servlet-mapping/servlet-name", 0);
//将web-app/servlet-mapping/url-pattern的值，作为方法的第二个参数
digester.addCallParam("web-app/servlet-mapping/url-pattern", 1);
// Process the web application deployment descriptor
if (log.isDebugEnabled()) {
log.debug("Scanning web.xml for controller servlet mapping");
}
//读取/WEB-INF/web.xml（写死的
InputStream input =
getServletContext().getResourceAsStream("/WEB-INF/web.xml");
if (input == null) {
log.error(internal.getMessage("configWebXml"));
throw new ServletException(internal.getMessage("configWebXml"));
}
try {
//解析xml，随后执行了前面的方法addServletMapping
digester.parse(input);
} catch (IOException e) {
log.error(internal.getMessage("configWebXml"), e);
throw new ServletException(e);
} catch (SAXException e) {
log.error(internal.getMessage("configWebXml"), e);
throw new ServletException(e);
} finally {
try {
input.close();
} catch (IOException e) {
log.error(internal.getMessage("configWebXml"), e);
throw new ServletException(e);
}
}
// Record a servlet context attribute (if appropriate)
if (log.isDebugEnabled()) {
log.debug("Mapping for servlet '" + servletName + "' = '"
+ servletMapping + "'");
}
if (servletMapping != null) {
//把struts1配置的url匹配字符串放入servletcontext中
getServletContext().setAttribute(Globals.SERVLET_KEY, servletMapping);
}
}
