-Xdebug

Enables remote debugging.

-Xnoagent

On a Sun VM, disables the proprietary debugging interface thus letting JPDA work correctly.在Sun VM上，禁用专有调试接口，从而允许JPDA正确工作。

-Djava.compiler=NONE

Disables Just-In-Time (JIT) compilation..

我们一般debug程序的时候，只是关注其中的一部分代码，而且大部分情况下是设置断点，然后单步执行，而JIT的编译单位是class，只要我们执行了class里面的代码，JIT就会对整个class进行编译，而我们实际执行的代码一般都是其中的一部分代码，所以从整个时间效率上来看，采用JIT反而更费时间。也就是说在JVM远程调试这个事情上，禁用JIT（只使用转译器，解释一行执行一条）更合理，所以通过-Djava.compiler=NONE来禁止JIT。

-Xrunjdwp:

transport=dt_socket,

server=y,

address=5000,

suspend=y

Loads JDWP (Java Debug Wire Protocol), the reference implementation of JPDA. Sub-options further specify the option.

transport=dt_socket

Sets the transport type for the connection with the debugging application; in this example, we will connect via a socket.

server=y

Tells the VM whether it must be receptive to an attaching debugging application.

address=5000

The port address for our connection; we will need 5000 for our example.

suspend=y

This option can be set depending on whether we want to suspend the exectution of the VM until a debugging application connects. This is useful if we seek to understand what happens when a server starts.