java程序获取绝对路径的代码！

前一段做个程序，遇到了这样一个问题，想利用相对路径删掉一个文件(实际存在的),老是删不掉. 真是急人呀，最后让我费了好大力气才算把它解决掉，问题不防跟大家说说，万一遇到这样的问题，就不用再费劲了！

情况是这样的：我的Tomcat装在了c盘，而我的虚拟目录设在了E:/work下，我在E:/work/test/image下有个图片，test.gif 我想通过程序删掉它，但他的绝对路径不确定(为了考虑到程序以后的移植,绝对路径是不确定的)。

假设del.jsp文件在e:/work/test 下，用下面的程序好像可以删掉：


<%@ page contentType="text/html; charset=GBK" errorPage="" %>
<%request.setCharacterEncoding("GBK");%>
<%@ page language="java" import="java.sql.*" import="java.util.*" import ="java.text.*" import="java.io.*"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GBK">
<title>删除成功页面</title>
</head>
<body>
File f=new File("/image/",test.gif);
boolean a=f.delete();
out.print("a="+a);
</body>
</html>

但事实上不行，你会发现a=false;

这就需要获取其绝对路径，我们用java程序来做一个专门来获取绝对路径的javaBean(path_test.java)就可以了。

path_test.java的代码如下：

package pathtest;
import java.io.*;
import javax.servlet.*;
import javax.servlet.jsp.PageContext;//导入PageContext类，不要忘了
public class path_test
{

protected ServletContext m_application;
private boolean m_denyPhysicalPath;
public path_test()
{

}
public final void initialize(PageContext pageContext)
throws ServletException
{
m_application = pageContext.getServletContext();

}

public String getPhysicalPath(String filePathName, int option)
throws IOException
{
String path = new String();
String fileName = new String();
String fileSeparator = new String();
boolean isPhysical = false;
fileSeparator=System.getProperty("file.separator");
if(filePathName == null)
throw new IllegalArgumentException("There is no specified destination file (1140).");
if(filePathName.equals(""))
throw new IllegalArgumentException("There is no specified destination file (1140).");
if(filePathName.lastIndexOf("\") >= 0)
{
path = filePathName.substring(0, filePathName.lastIndexOf("\"));
fileName = filePathName.substring(filePathName.lastIndexOf("\") + 1);
}
if(filePathName.lastIndexOf("/") >= 0)
{
path = filePathName.substring(0, filePathName.lastIndexOf("/"));
fileName = filePathName.substring(filePathName.lastIndexOf("/") + 1);
}
path = path.length() != 0 ? path : "/";
java.io.File physicalPath = new java.io.File(path);
if(physicalPath.exists())
isPhysical = true;
if(option == 0)
{
if(isVirtual(path))
{
path = m_application.getRealPath(path);
if(path.endsWith(fileSeparator))
path = path + fileName;
else
path = String.valueOf((new StringBuffer(String.valueOf(path))).append(fileSeparator).append(fileName));
return path;
}
if(isPhysical)
{
if(m_denyPhysicalPath)
throw new IllegalArgumentException("Physical path is denied (1125).");
else
return filePathName;
} else
{
throw new IllegalArgumentException("This path does not exist (1135).");
}
}
if(option == 1)
{
if(isVirtual(path))
{
path = m_application.getRealPath(path);
if(path.endsWith(fileSeparator))
path = path + fileName;
else
path = String.valueOf((new StringBuffer(String.valueOf(path))).append(fileSeparator).append(fileName));
return path;
}
if(isPhysical)
throw new IllegalArgumentException("The path is not a virtual path.");
else
throw new IllegalArgumentException("This path does not exist (1135).");
}
if(option == 2)
{
if(isPhysical)
if(m_denyPhysicalPath)
throw new IllegalArgumentException("Physical path is denied (1125).");
else
return filePathName;
if(isVirtual(path))
throw new IllegalArgumentException("The path is not a physical path.");
else
throw new IllegalArgumentException("This path does not exist (1135).");
}

else
{
return null;
}

}
private boolean isVirtual(String pathName) //判断是否是虚拟路径
{
if(m_application.getRealPath(pathName) != null)
{
java.io.File virtualFile = new java.io.File(m_application.getRealPath(pathName));
return virtualFile.exists();
}

else
{
return false;
}
}

}

对path_test.java编译后，得到包pathtest,里面有path_test.class类，

把整个包放到虚拟目录的classes下，然后再把del.jsp文件改成如下程序，一切都OK了！


<%@ page contentType="text/html; charset=GBK" errorPage="" %>
<%request.setCharacterEncoding("GBK");%>
<%@ page language="java" import="java.sql.*" import="java.util.*" import ="java.text.*" import="java.io.*"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GBK">
<title>删除成功页面</title>
</head>
<body>
<jsp:useBean id="pathtest" scope="page" class="pathtest.path_test" />
pathtest.initialize(pageContext);//初始化
String dir1=pathtest.getPhysicalPath("/test/image/",0);//传参数
out.print(dir1);//输出的是绝对路径
File file=new File(dir1,"test.gif");//生成文件对象
boolean a=file.delete();
out.print("a="+a);
</body">
</html>

此时a=true;表示删除成功！

到此为止，问题全部搞定。