web项目访问jsp路径 Servlet及相关类和接口(2)

可以看到，Servlet接口里面只有五个方法：init()、getServletConfig()、service()、getServletInfo()、destroy()。其中init()、service()、destroy()三个方法是和servlet生命周期相关的方法，在生命周期的不同时间段内会执行不同的方法，其顺序是init()->service()->destroy()。其中init()、destroy()方法在servlet生命周期中都只执行一次，而service()方法可以多次执行。Servlet接口是Servlet类最底层、最基础、最重要的接口。

3、ServletConfig接口

先看源码：

package javax.servlet;

import java.util.Enumeration;

public abstract interface ServletConfig {
    public abstract String getServletName();

    public abstract ServletContext getServletContext();

    public abstract String getInitParameter(String paramString);

    public abstract Enumeration<String> getInitParameterNames();
}

getServletName()：获取web.xml文件里面的servlet的名字（即<servlet-name>标签配置的名字）。

getServletContext()：获取ServletContext对象，下面会介绍ServletContext接口。

getInitParameter()：获取web.xml文件在servlet标签中配置的参数值（注意是servlet标签，而不是其他标签配置的参数值）。

getInitParameterNames()：获取在Servlet中所有初始化参数的名字，也就是key值，可以通过key值，来找到各个初始化参数的value值（注意返回的是枚举类型）。

可以看到，ServletConfig接口里面的方法主要是获取web.xml文件里和servlet相关的配置信息。web项目访问jsp路径

4、ServletContext接口

先看源码：

package javax.servlet;

import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.EventListener;
import java.util.Map;
import java.util.Set;
import javax.servlet.descriptor.JspConfigDescriptor;

public abstract interface ServletContext {
    public static final String TEMPDIR = "javax.servlet.context.tempdir";
    public static final String ORDERED_LIBS = "javax.servlet.context.orderedLibs";

    public abstract ServletContext getContext(String paramString);

    public abstract String getContextPath();

    public abstract int getMajorVersion();

    public abstract int getMinorVersion();

    public abstract int getEffectiveMajorVersion();

    public abstract int getEffectiveMinorVersion();

    public abstract String getMimeType(String paramString);

    public abstract Set<String> getResourcePaths(String paramString);

    public abstract URL getResource(String paramString)
            throws MalformedURLException;

    public abstract InputStream getResourceAsStream(String paramString);

    public abstract RequestDispatcher getRequestDispatcher(String paramString);

    public abstract RequestDispatcher getNamedDispatcher(String paramString);

    public abstract Servlet getServlet(String paramString)
            throws ServletException;

    public abstract Enumeration<Servlet> getServlets();

    public abstract Enumeration<String> getServletNames();

    public abstract void log(String paramString);

    public abstract void log(Exception paramException, String paramString);

    public abstract void log(String paramString, Throwable paramThrowable);

    public abstract String getRealPath(String paramString);

    public abstract String getServerInfo();

    public abstract String getInitParameter(String paramString);

    public abstract Enumeration<String> getInitParameterNames();

    public abstract boolean setInitParameter(String paramString1,
            String paramString2);

    public abstract Object getAttribute(String paramString);

    public abstract Enumeration<String> getAttributeNames();

    public abstract void setAttribute(String paramString, Object paramObject);

    public abstract void removeAttribute(String paramString);

    public abstract String getServletContextName();

    public abstract ServletRegistration.Dynamic addServlet(String paramString1,
            String paramString2);

    public abstract ServletRegistration.Dynamic addServlet(String paramString,
            Servlet paramServlet);

    public abstract ServletRegistration.Dynamic addServlet(String paramString,
            Class<? extends Servlet> paramClass);

    public abstract <T extends Servlet> T createServlet(Class<T> paramClass)
            throws ServletException;

    public abstract ServletRegistration getServletRegistration(
            String paramString);

    public abstract Map<String, ? extends ServletRegistration> getServletRegistrations();

    public abstract FilterRegistration.Dynamic addFilter(String paramString1,
            String paramString2);

    public abstract FilterRegistration.Dynamic addFilter(String paramString,
            Filter paramFilter);

    public abstract FilterRegistration.Dynamic addFilter(String paramString,
            Class<? extends Filter> paramClass);

    public abstract <T extends Filter> T createFilter(Class<T> paramClass)
            throws ServletException;

    public abstract FilterRegistration getFilterRegistration(String paramString);

    public abstract Map<String, ? extends FilterRegistration> getFilterRegistrations();

    public abstract SessionCookieConfig getSessionCookieConfig();

    public abstract void setSessionTrackingModes(
            Set<SessionTrackingMode> paramSet) throws IllegalStateException,
            IllegalArgumentException;

    public abstract Set<SessionTrackingMode> getDefaultSessionTrackingModes();

    public abstract Set<SessionTrackingMode> getEffectiveSessionTrackingModes();

    public abstract void addListener(String paramString);

    public abstract <T extends EventListener> void addListener(T paramT);

    public abstract void addListener(Class<? extends EventListener> paramClass);

    public abstract <T extends EventListener> T createListener(
            Class<T> paramClass) throws ServletException;

    public abstract void declareRoles(String[] paramArrayOfString);

    public abstract ClassLoader getClassLoader();

    public abstract JspConfigDescriptor getJspConfigDescriptor();
}

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