从嵌套Hashmap获取键和值

Question

So, I'm creating a nested hash map for two switches using the switches ID and then putting in a source Mac address and a port.

Eg switch1 should contain its own mappings, as should switch2 and both switches should obviously communicate with each other, so I've set the HashMap up like so:

HashMap<String, HashMap<Long, Short>> map = new HashMap<String, HashMap<Long,Short>>();

if(sw.getId() == 1){
        switchMap.put("1", new HashMap<Long, Short>());
        switchMap.get("1").put(sourceMac, (short) pi.getInPort());
}
else if(sw.getId() == 2){
        switchMap.put("2", new HashMap<Long, Short>());
        switchMap.get("2").put(sourceMac, (short) pi.getInPort());
}

Now, what I would like to do is check each switch's key (either 1 or 2) and then check that each switch has the correct sourceMac and port# when checking a given destinationMac:

Long destinationMac = Ethernet.toLong(match.getDataLayerDestination());

if (switchMap.containsKey("1") && switchMap.containsValue(destinationMac)) {    
    /* Now we can retrieve the port number. This will be the port that we need to send the
    packet over to reach the host to which that MAC address belongs. */
    short destinationPort = (short) switchMap.get("1").get(destinationMac);
    /*Write the packet to a port, use the destination port we have just found.*/
    installFlowMod(sw, pi, match, destinationPort, 50, 100, cntx);
} 
else if (switchMap.containsKey("2") && switchMap.containsValue(destinationMac)) {   
    /* Now we can retrieve the port number. This will be the port that we need to send the
    packet over to reach the host to which that MAC address belongs. */
    short destinationPort = (short) switchMap.get("2").get(destinationMac)
    /*Write the packet to a port, use the destination port we have just found.*/
    installFlowMod(sw, pi, match, destinationPort, 50, 100, cntx);
}
else {
    log.debug("Destination MAC address unknown: flooding");
    writePacketToPort(sw, pi, OFPort.OFPP_FLOOD.getValue(), cntx);
}

When I run the code and try to ping from h1(switch1) to h3(switch2) I get requests back, but I still get the error message "Destination MAC address unknown: flooding"

My question is, am I getting the values from the nested HashMap correctly? Or is my logic completely messed up?

Answer 1

for(String s: map.keySet()){
    HashMap<Long, Short> switchMap =map.get(s);
    if(switchMap.containsValue(destinationMac)){ 
        return switchMap.get(destinationMac);
    }
}

Answer 2

The way you're checking the presence of the destination address is wrong. It should be something like:

Short portS1 = switchMap.get("1").get(destinationMac)
if (portS1 != null) {
  installFlowMod(sw, pi, match, portS1, 50, 100, cntx);
}

Short portS2 = switchMap.get("1").get(destinationMac)
if (portS2 != null) {
  installFlowMod(sw, pi, match, portS2, 50, 100, cntx);
}

For this to work you have to initialize all your switch mapping with an empty Map<Long, Short> .

An even more generic approach would be this:

for (Map.Entry<String, Map<Long, Short>> e: switchMap.entrySet()) {
  Short port = e.getValue().get(destinationMac);
  if (port != null) installFlowMod(sw, pi, match, port, 50, 100, cntx); 
}

Doing it this way you do not even need to pre-initialize the switchMap.