ServletContext中getRealPath()读取文件及其他三种读取文件的方式及其区别
前提条件：
1，新建webproiect为20140806-servlet-servletresponse-servletrequest
2，第一个配置文件是在工程的src根目录下建立filesrc.properties。并且里面的键值对为：src=filesrc
3，第二个配置文件在src目录的包com.itheima.servletcontext.fourreadresource中建立filecom.properties,并且里面的键值对为：com=filecom
4,第三个配置文件在WEB-INF的根目录下建立filewebinf.properties，里面的键值对为：webinf=filewebinf
建立好之后如图：
下面是具体的代码实现：
package com.itheima.servletcontext.fourreadresource;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Properties;
import java.util.ResourceBundle;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ReadPrepertiesServletContextDemo7 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//test00();
//test01();
//test02();
//test10();
//test11();
//test21();
//test22();
//test23();
test30();
}
<span style="white-space:pre"></span>//按照倒序，第四种在上面，servletcontext的getRealPath方法在最后//=============================================================================================//通过类加载器 ,默认一上来就已经定位到classes目录//通过URL来获取文件的路径private void test30() throws FileNotFoundException, IOException {ClassLoader cl=this.getClass().getClassLoader();URL url=cl.getResource("filesrc.properties");String path=url.getPath();Properties prop=new Properties();prop.load(new FileInputStream(path));System.out.println(prop.getProperty("src"));//}//=============================================================================================//通过类加载器 ,默认一上来就已经定位到classes目录private void test21() throws FileNotFoundException, IOException {ClassLoader cl=this.getClass().getClassLoader();InputStream ins=cl.getResourceAsStream("filesrc.properties");Properties prop=new Properties();prop.load(ins);System.out.println(prop.getProperty("src"));}//通过类加载器 ,获取classes目录下的包里的配置文件private void test22() throws FileNotFoundException, IOException {ClassLoader cl=this.getClass().getClassLoader();//此处需要把包名的.换成/InputStream ins=cl.getResourceAsStream("com/itheima/servletcontext/fourreadresource/filecom.properties");Properties prop=new Properties();prop.load(ins);System.out.println(prop.getProperty("com"));}//通过类加载器 ,获取classes上上一级目录下的配置文件private void test23() throws FileNotFoundException, IOException {ClassLoader cl=this.getClass().getClassLoader();//此处需要把包名的.换成/InputStream ins=cl.getResourceAsStream("../../filewebinf.properties");Properties prop=new Properties();prop.load(ins);System.out.println(prop.getProperty("webinf"));}//=============================================================================================//注意:ResourceBundle它只能读取src下的资源(classes目录)，可以是web项目，也可以java项目private void test10() throws FileNotFoundException, IOException {ResourceBundle rb=ResourceBundle.getBundle("filesrc");//基名:不带扩展名的src目录下的文件System.out.println(rb.getString("src"));}//ResourceBundlesrc下的包中的资源，可以是web项目，也可以java项目private void test11() throws FileNotFoundException, IOException {ResourceBundle rb=ResourceBundle.getBundle("com.itheima.servletcontext.fourreadresource.filecom");//基名:不带扩展名的src目录下的文件System.out.println(rb.getString("com"));}//=====================================================================================================//方式一：采用ServletContext的getRealPath()读取src目录下的配置文件//这个方式只能用于web项目private void test00() throws FileNotFoundException, IOException {//获取ServletContext对象ServletContext sc=getServletContext();//获取文件的绝对路径，并且绝对路径都是以/开头的String path=sc.getRealPath("/WEB-INF/classes/filesrc.properties");//获取Properties对象，读取配置文件的key-value--一下代码都是不变的Properties prop=new Properties();InputStream ins=new FileInputStream(new File(path));prop.load(ins);System.out.println(prop.getProperty("src"));//prop.load(new FileInputStream(getServletContext().getRealPath("/WEB-INF/classes/filesrc.properties")));}//方式一：采用ServletContext读取包目录下的配置文件，只需要把路径改一下即可private void test01() throws FileNotFoundException, IOException {//获取ServletContext对象ServletContext sc=getServletContext();//获取文件的绝对路径，并且绝对路径都是以/开头的//需要把包名的.全部改成/。这是绝对路径String path=sc.getRealPath("/WEB-INF/classes/com/itheima/servletcontext/fourreadresource/filecom.properties");//获取Properties对象，读取配置文件的key-value--一下代码都是不变的Properties prop=new Properties();InputStream ins=new FileInputStream(new File(path));prop.load(ins);System.out.println(prop.getProperty("com"));}//方式一：采用ServletContext读取WEB-INF目录下的配置文件，只需要把路径改一下即可private void test02() throws FileNotFoundException, IOException {//获取ServletContext对象ServletContext sc=getServletContext();//获取文件的绝对路径，并且绝对路径都是以/开头的String path=sc.getRealPath("/filewebinf.properties");//获取Properties对象，读取配置文件的key-value--一下代码都是不变的Properties prop=new Properties();InputStream ins=new FileInputStream(new File(path));prop.load(ins);System.out.println(prop.getProperty("webinf"));}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}}