02ServletConfig、ServletContext

ServletConfig

• 封装了Servlet的配置信息

  • 配置Servlet的初始化参数

    <servlet>    <init-param>        <param-name>user</param-name>        <param-value>root</param-value>    </init-param>    <init-param>        <param-name>password</param-name>        <param-value>1234</param-value>    </init-param></servlet>

    注意：配置在元素前，否则会报错

  • 获取初始化参数

    • getInitParamter(String name)：获取指定参数名的初始化参数

    • getInitParamterNames():获取参数名组成的Enumeration对象

      Enumeration<String> names = servletConfig.getInitParameterNames();while(names.hasMoreElements()){    String name = names.nextElement();  //获取name属性的值    String value = servletConfig.getInitParameter(name);    //name所对应的value属性的值    System.out.println(name+":"+value);}

  • 获取Servlet的配置名称

    • String servletName = servletConfig.getServletName();

• 可以获取ServletContext对象

ServletContext

• 可以由ServletConfig获取

  ServletContext servletContext = servletConfig.getServletContext();

• 代表当前web运用

  • 获取当前web应用的初始化参数

    <context-param>    <param-name>driver</param-name>    <param-value>com.mysql.jdbc.Driver</param-value></context-param>

  • 获取当前web应用的某一个文件在服务器上的绝对路径

    • getRealPath(String path);

      ServletContext servletContext = servletConfig.getServletContext();String driver = servletContext.getInitParameter("driver");Enumeration<String> names2 = servletContext.getInitParameterNames();while(names.hasMoreElements()){    String name = names2.nextElement(); //获取name属性的值    System.out.println("servletContext--name--"+name);}

  • 获取当前web应用的名称

    • getContextPath()

      String contextPath = servletContext.getContextPath();System.out.println("contextPath: "+contextPath);

  • 获取当前web应用的某个文件对应的输入流

    • getResourceAsStream(String path):path的“/”为当前web应用的根目录

      ClassLoader classLoader = getClass().getClassLoader();InputStream is = classLoader.getResourceAsStream("jdbc.peoperties");System.out.println("1."+is);InputStream is2 = servletContext.getResourceAsStream("/WEB-INF/classes/jdbc.properties");System.out.println("2."+is2);