绝对路径：是从盘符开始的路径，形如 // 多用在后台中
C:windowssystem32cmd.exe
相对路径：是从当前路径开始的路径 //多用在前端
/开头的通常表示绝对路径:
/表示站点路径的场景如下（其他情况是在服务器上跳转 / 表示项目的根）
(1) 重定向
(2) 超链接
(3) action表单
在web项目中，为了安全，可能需要把jsp文件放在WEB-INF目录下，这样如果我们的页面中出现超链接a标签或者js的location.href去直接转向到WEB-INF下的某一个jsp页面，那么就会引用不到，因为这样的请求方式是客户端的请求，而WEB-INF页面只对服务端开放，对客户端是不可见的。（只能通过转发的方式进入）
1 超链接
<body>
<a href="/tiaozhuan/views/index.jsp">超链接jsp跳转</a> //进入jsp页面
<a href="/tiaozhuan/servletA">超链接跳服务器(注解)</a>
<a href="/tiaozhuan/servletB">超链接跳服务器(web.xml)</a>
</body>
(1) 方式1 通过注解进入servlet
@WebServlet("/servletA")
public class ChaoLianJieServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("doGet"+Thread.currentThread().getName());
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("doPost"+Thread.currentThread().getName());
//doGet(req, resp);
}
（2） 方式2 通过web.xml配置进入servlet
public class ChaoLianjieServlet1 extends HttpServlet{
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println("ChaoLianjieServlet1 +doPost");
doGet(req, resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
doPost(req, resp);
}
}
web.xml
<servlet>
<servlet-name>servletB</servlet-name>
<servlet-class>com.rl.chaolianjie.ChaoLianjieServlet1</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>servletB</servlet-name>
<url-pattern>/servletB</url-pattern>
</servlet-mapping>
action ：
<form method="post" action="/tiaozhuan/servletB">
<input type="submit" value="submit"/>
</form>
<servlet>
<servlet-name>servletB</servlet-name>
<servlet-class>com.rl.chaolianjie.ChaoLianjieServlet1</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>servletB</servlet-name>
<url-pattern>/servletB</url-pattern>
</servlet-mapping>
public class ChaoLianjieServlet1 extends HttpServlet{
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println("ChaoLianjieServlet1 +doPost");
//doGet(req, resp);
}
}
重定向和转发：
<form method="post" action="/tiaozhuan/servletA">
<input type="submit" value="submit1"/>
</form>
<form method="get" action="/tiaozhuan/servletA">
<input type="submit" value="submit2"/>
</form>
@WebServlet("/servletA")
public class ChaoLianJieServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.sendRedirect("/tiaozhuan/views/index.jsp");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.getRequestDispatcher("/views/index.jsp").forward(req, resp);
}
读取文件/获取初始化参数：
1 配置
<servlet> <servlet-name>servletB</servlet-name> <servlet-class>com.rl.chaolianjie.ChaoLianjieServlet1</servlet-class> <init-param> <param-name>name</param-name> <param-value>zhang</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet>
2 获取
String path=getServletContext().getRealPath("/file/web.xml"); System.out.println(path); BufferedReader br=new BufferedReader( new FileReader(new File(path))); System.out.println(br.readLine()); //获取初始化参数 String name=getServletContext().getInitParameter("name"); String nameconf=getServletConfig().getInitParameter("name"); resp.getWriter().print(name+"getServletContext");//null resp.getWriter().print(nameconf+"getServletConfig");//有值
1.FileTest.class.getResource("")
得到的是当前类FileTest.class文件的URI目录。不包括自己！
如：file:/D:/java/eclipse32/workspace/jbpmtest3/bin/com/test/
2.FileTest.class.getResource("/")
得到的是当前的classpath的绝对URI路径。
如：file:/D:/java/eclipse32/workspace/jbpmtest3/bin/
3.Thread.currentThread().getContextClassLoader().getResource("")
得到的也是当前ClassPath的绝对URI路径。
如：file:/D:/java/eclipse32/workspace/jbpmtest3/bin/
4.FileTest.class.getClassLoader().getResource("")
得到的也是当前ClassPath的绝对URI路径。
服务器上：没加 /
System.out.println("bb"+Thread.currentThread().getContextClassLoader().getResource(""));
System.out.println("cc"+ChaoLianJieServlet.class.getResource(""));
bbfile:/D:/work/eclipse/workspaceOne/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/tiaozhuan/WEB-INF/classes/
ccfile:/D:/work/eclipse/workspaceOne/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/tiaozhuan/WEB-INF/classes/com/rl/chaolianjie/
服务器上 ： 加 了/
System.out.println("aa"+Thread.currentThread().getContextClassLoader().getResource("/"));
System.out.println("dd"+ChaoLianJieServlet.class.getResource("/"));
aafile:/D:/work/eclipse/workspaceOne/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/tiaozhuan/WEB-INF/classes/
ddfile:/D:/work/eclipse/workspaceOne/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/tiaozhuan/WEB-INF/classes/
本地：
URL path=FileResourse.class.getResource("/");
System.out.println(path); // file:/D:/work/eclipse/workspaceOne/tiaozhuan/build/classes/
URL path1=FileResourse.class.getResource("");
System.out.println(path1); //file:/D:/work/eclipse/workspaceOne/tiaozhuan/build/classes/com/rl/chaolianjie/
URL a=Thread.currentThread().getContextClassLoader().getResource("");
System.out.println(a); //file:/D:/work/eclipse/workspaceOne/tiaozhuan/build/classes/
URL b= Thread.currentThread().getContextClassLoader().getResource("/");
System.out.println(b); null
URL c=Thread.currentThread().getClass().getResource("");
System.out.println(c); null
URL path2 = Thread.currentThread().getContextClassLoader().getResource("/");
URL path3 = Thread.currentThread().getContextClassLoader().getResource("");
System.out.println(path2); null
System.out.println(path3); file:/D:/work/eclipse/workspaceOne/tiaozhuan/build/classes/
服务器上：加了/ Thread.currentThread().getContextClassLoader().getResource("/")和当前类.class.getResource("/")的值都是classpath的绝对URI路径
不加/ Thread.currentThread().getContextClassLoader().getResource("")得到的是classpath的绝对URI路径 而当前类.class.getResource("")的值是包结构下
本地 加了/ 当前类.class.getResource("/") 是classpath 下绝对URI ， Thread.currentThread().getContextClassLoader().getResource("/")是null
不加/ 当前类.class.getResource("")是当前孢结构下 T hread.currentThread().getContextClassLoader().getResource("") 是 classpath 下 绝对URI 路径