使用 Java 进行 CLI 模式匹配

Question

Problem Statement

I'm working on a use case where I have a set of commands supported on a device and actual commands that I want to execute.

Commands Supported (Sample)

config dhcp ip <dhcp-ipaddress> port <dhcp-port-number>
config dhcp ip <dhcp-ipaddress> timeout <time-out-value>
config dhcp ipv4 <dhcp-ipaddress>
config dns ip <dns-ipaddress> port <dns-port-number>
config dns ip <dns-ipaddress> timeout <time-out-value>
config router bgp <bgp-number>
config interface id <interface-id> 
config interface name <interface-name> id <interface-id>

Actual Commands (Sample)

config dhcp ip 1.1.1.1 port 8080
config dhcp ip 1.1.1.2 timeout 120
config dhcp ip 1.1.1.1 timeout 120
config dhcp ip 1.1.1.2 port 8080
config dhcp ipv4 1.1.1.3
config interface id 12 
config interface name abc id 12
config interface id 13 
config interface name xyz id 13

<> are the placeholders for the values the commands can take and others are keywords. Also, all the placeholders will be the same for a given entity, for instance will a common placeholder in all the commands which take DHCP addresses.

Expected Output

I have to match the "actual commands" with the "commands supported" and then group them based on the values in the placeholders in the same order something like this.

config dhcp ip 1.1.1.1 port 8080
config dhcp ip 1.1.1.1 timeout 120

config dhcp ip 1.1.1.2 timeout 120
config dhcp ip 1.1.1.2 port 8080

config dhcp ipv4 1.1.1.3

config interface id 12 
config interface name abc id 12

config interface id 13 
config interface name xyz id 13

I am trying to achieve this with Regex matching but want to know if there is a better way to do it. Also, the commands supported and actual commands could be huge, so looking for a time-efficient approach.

Answer 1

I'm guessing that maybe regular expression wouldn't be the best idea here, or you are going to at least have a combined regex-coding method to solve the problem.

The following exampled expression is showing that, "kind of", how a regular expression can be designed or how you might approach solving the problem with that, if you wish so.

^config d(hcp|ns) ip(v4)? (<[^>]*>|(?:\\d+\\.){3}\\d+)( port| timeout|\\s*$)( <[^>]*>\\s*$| \\d+\\s*$|\\s*$)|config (router|interface) (id|bgp|name) (<[^>]*>\\s*$|<[^>]*> id <[^>]*>\\s*$|\\d+\\s*$|[a-z]+ id \\d+\\s*$|\\s*$)

which can be simplified to,

^config (dhcp|dns|router|interface) (?:ip|ipv4|id|bgp|name) (<[^>]*>|(?:\\d+\\.){3}\\d+|[a-z]+ id \\d+|\\d+)( port| timeout| id|\\s*)( <[^>]*>\\s*| \\d+\\s*|\\s*)$

Demo

It's not complicated, is just verbose to write an expression like that.

Test

import java.util.regex.Matcher;
import java.util.regex.Pattern;


public class RegularExpression{

    public static void main(String[] args){

        final String regex = "^config (dhcp|dns|router|interface) (?:ip|ipv4|id|bgp|name) (<[^>]*>|(?:\\d+\\.){3}\\d+|[a-z]+ id \\d+|\\d+)( port| timeout| id|\\s*)( <[^>]*>\\s*| \\d+\\s*|\\s*)$";
        final String string = "config dhcp ip <dhcp-ipaddress> port <dhcp-port-number>\n"
             + "config dhcp ip <dhcp-ipaddress> timeout <time-out-value>\n"
             + "config dhcp ipv4 <dhcp-ipaddress>\n"
             + "config dns ip <dns-ipaddress> port <dns-port-number>\n"
             + "config dns ip <dns-ipaddress> timeout <time-out-value>\n"
             + "config router bgp <bgp-number>\n"
             + "config interface id <interface-id> \n"
             + "config interface name <interface-name> id <interface-id>\n\n"
             + "config dhcp ip 1.1.1.1 port 8080\n"
             + "config dhcp ip 1.1.1.2 timeout 120\n"
             + "config dhcp ip 1.1.1.1 timeout 120\n"
             + "config dhcp ip 1.1.1.2 port 8080\n"
             + "config dhcp ipv4 1.1.1.3\n"
             + "config interface id 12 \n"
             + "config interface name abc id 12\n"
             + "config interface id 13 \n"
             + "config interface name xyz id 13\n\n"
             + "config dhcp ip 1.1.1.1 port 8080\n"
             + "config dhcp ip 1.1.1.1 timeout 120\n"
             + "config dhcp ip 1.1.1.2 timeout 120\n"
             + "config dhcp ip 1.1.1.2 port 8080\n"
             + "config dhcp ipv4 1.1.1.3\n"
             + "config interface id 12 \n"
             + "config interface name abc id 12\n"
             + "config interface id 13 \n"
             + "config interface name xyz id 13";

        final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
        final Matcher matcher = pattern.matcher(string);

        while (matcher.find()) {
            System.out.println("Full match: " + matcher.group(0));
            for (int i = 1; i <= matcher.groupCount(); i++) {
                System.out.println("Group " + i + ": " + matcher.group(i));
            }
        }


    }
}

Output

Full match: config dhcp ip <dhcp-ipaddress> port <dhcp-port-number>
Group 1: dhcp
Group 2: <dhcp-ipaddress>
Group 3:  port
Group 4:  <dhcp-port-number>
Full match: config dhcp ip <dhcp-ipaddress> timeout <time-out-value>
Group 1: dhcp
Group 2: <dhcp-ipaddress>
Group 3:  timeout
Group 4:  <time-out-value>
Full match: config dhcp ipv4 <dhcp-ipaddress>
Group 1: dhcp
Group 2: <dhcp-ipaddress>
Group 3: 
Group 4: 
Full match: config dns ip <dns-ipaddress> port <dns-port-number>
Group 1: dns
Group 2: <dns-ipaddress>
Group 3:  port
Group 4:  <dns-port-number>
Full match: config dns ip <dns-ipaddress> timeout <time-out-value>
Group 1: dns
Group 2: <dns-ipaddress>
Group 3:  timeout
Group 4:  <time-out-value>
Full match: config router bgp <bgp-number>
Group 1: router
Group 2: <bgp-number>
Group 3: 
Group 4: 
Full match: config interface id <interface-id> 
Group 1: interface
Group 2: <interface-id>
Group 3:  
Group 4: 
Full match: config interface name <interface-name> id <interface-id>

Group 1: interface
Group 2: <interface-name>
Group 3:  id
Group 4:  <interface-id>

Full match: config dhcp ip 1.1.1.1 port 8080
Group 1: dhcp
Group 2: 1.1.1.1
Group 3:  port
Group 4:  8080
Full match: config dhcp ip 1.1.1.2 timeout 120
Group 1: dhcp
Group 2: 1.1.1.2
Group 3:  timeout
Group 4:  120
Full match: config dhcp ip 1.1.1.1 timeout 120
Group 1: dhcp
Group 2: 1.1.1.1
Group 3:  timeout
Group 4:  120
Full match: config dhcp ip 1.1.1.2 port 8080
Group 1: dhcp
Group 2: 1.1.1.2
Group 3:  port
Group 4:  8080
Full match: config dhcp ipv4 1.1.1.3
Group 1: dhcp
Group 2: 1.1.1.3
Group 3: 
Group 4: 
Full match: config interface id 12 
Group 1: interface
Group 2: 12
Group 3:  
Group 4: 
Full match: config interface name abc id 12
Group 1: interface
Group 2: abc id 12
Group 3: 
Group 4: 
Full match: config interface id 13 
Group 1: interface
Group 2: 13
Group 3:  
Group 4: 
Full match: config interface name xyz id 13

Group 1: interface
Group 2: xyz id 13
Group 3: 

Group 4: 
Full match: config dhcp ip 1.1.1.1 port 8080
Group 1: dhcp
Group 2: 1.1.1.1
Group 3:  port
Group 4:  8080
Full match: config dhcp ip 1.1.1.1 timeout 120
Group 1: dhcp
Group 2: 1.1.1.1
Group 3:  timeout
Group 4:  120
Full match: config dhcp ip 1.1.1.2 timeout 120
Group 1: dhcp
Group 2: 1.1.1.2
Group 3:  timeout
Group 4:  120
Full match: config dhcp ip 1.1.1.2 port 8080
Group 1: dhcp
Group 2: 1.1.1.2
Group 3:  port
Group 4:  8080
Full match: config dhcp ipv4 1.1.1.3
Group 1: dhcp
Group 2: 1.1.1.3
Group 3: 
Group 4: 
Full match: config interface id 12 
Group 1: interface
Group 2: 12
Group 3:  
Group 4: 
Full match: config interface name abc id 12
Group 1: interface
Group 2: abc id 12
Group 3: 
Group 4: 
Full match: config interface id 13 
Group 1: interface
Group 2: 13
Group 3:  
Group 4: 
Full match: config interface name xyz id 13
Group 1: interface
Group 2: xyz id 13
Group 3: 
Group 4: 

RegEx Circuit

jex.im visualizes regular expressions:

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If you wish to simplify/modify/explore the expression, it's been explained on the top right panel of regex101.com . If you'd like, you can also watch in this link , how it would match against some sample inputs.

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A likely better approach might be to split your patterns and accordingly your samples, and then write few efficient methods with your desired data structure, then feed your samples through those methods.