| 1 | package dolda.jsvc; |
| 2 | |
| 3 | import java.util.*; |
| 4 | |
| 5 | public class ContextParam<T> { |
| 6 | private boolean bound; |
| 7 | private T value; |
| 8 | private final Object id = new Object(); |
| 9 | private Map<ThreadContext, T> perctx = new WeakHashMap<ThreadContext, T>(); |
| 10 | private Map<Thread, T> perthr = new WeakHashMap<Thread, T>(); |
| 11 | |
| 12 | public ContextParam(T def) { |
| 13 | this.value = def; |
| 14 | this.bound = true; |
| 15 | } |
| 16 | |
| 17 | public ContextParam() { |
| 18 | this.bound = false; |
| 19 | } |
| 20 | |
| 21 | public synchronized T get() { |
| 22 | Thread th = Thread.currentThread(); |
| 23 | if(perthr.containsKey(th)) |
| 24 | return(perthr.get(th)); |
| 25 | ThreadContext ctx = ThreadContext.current(); |
| 26 | if(perctx.containsKey(ctx)) |
| 27 | return(perctx.get(ctx)); |
| 28 | if(!bound) |
| 29 | throw(new IllegalStateException("No value is bound to this parameter.")); |
| 30 | return(value); |
| 31 | } |
| 32 | |
| 33 | public synchronized T ctxset(T val) { |
| 34 | ThreadContext ctx = ThreadContext.current(); |
| 35 | return(perctx.put(ctx, val)); |
| 36 | } |
| 37 | |
| 38 | public static Responder let(final Responder next, Object... params) { |
| 39 | final Map<ContextParam, Object> values = new HashMap<ContextParam, Object>(); |
| 40 | if((params.length % 2) != 0) |
| 41 | throw(new IllegalArgumentException("SvcConfig.let takes only an even number of parameters")); |
| 42 | for(int i = 0; i < params.length; i += 2) |
| 43 | values.put((ContextParam)params[i], params[i + 1]); |
| 44 | |
| 45 | return(new Responder() { |
| 46 | /* This can very well actually be set to something |
| 47 | * of the wrong type, but since the result would, |
| 48 | * obviously, be a ClassCastException either way, |
| 49 | * this way is at least the more convenient. */ |
| 50 | @SuppressWarnings("unchecked") |
| 51 | public void respond(Request req) { |
| 52 | final Map<ContextParam, Object> old = new HashMap<ContextParam, Object>(); |
| 53 | Thread th = Thread.currentThread(); |
| 54 | for(Map.Entry<ContextParam, Object> val : values.entrySet()) { |
| 55 | ContextParam p = val.getKey(); |
| 56 | synchronized(p) { |
| 57 | if(p.perthr.containsKey(th)) |
| 58 | old.put(p, p.perthr.get(th)); |
| 59 | p.perthr.put(th, val.getValue()); |
| 60 | } |
| 61 | } |
| 62 | try { |
| 63 | next.respond(req); |
| 64 | } finally { |
| 65 | for(Map.Entry<ContextParam, Object> val : values.entrySet()) { |
| 66 | ContextParam p = val.getKey(); |
| 67 | synchronized(p) { |
| 68 | if(old.containsKey(p)) { |
| 69 | p.perthr.put(th, old.get(p)); |
| 70 | } else { |
| 71 | p.perthr.remove(th); |
| 72 | } |
| 73 | } |
| 74 | } |
| 75 | } |
| 76 | } |
| 77 | }); |
| 78 | } |
| 79 | } |