01: /*<
02: * Copyright 2002-2007 the original author or authors.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
10: * Unless required by applicable law or agreed to in writing, software
11: * distributed under the License is distributed on an "AS IS" BASIS,
12: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13: * See the License for the specific language governing permissions and
14: * limitations under the License.
15: */
16:
17: package org.springframework.aop;
18:
19: /**
20: * A <code>TargetSource</code> is used to obtain the current "target" of
21: * an AOP invocation, which will be invoked via reflection if no around
22: * advice chooses to end the interceptor chain itself.
23: *
24: * <p>If a <code>TargetSource</code> is "static", it will always return
25: * the same target, allowing optimizations in the AOP framework. Dynamic
26: * target sources can support pooling, hot swapping, etc.
27: *
28: * <p>Application developers don't usually need to work with
29: * <code>TargetSources</code> directly: this is an AOP framework interface.
30: *
31: * @author Rod Johnson
32: */
33: public interface TargetSource extends TargetClassAware {
34:
35: /**
36: * Return the type of targets returned by this {@link TargetSource}.
37: * <p>Can return <code>null</code>, although certain usages of a
38: * <code>TargetSource</code> might just work with a predetermined
39: * target class.
40: * @return the type of targets returned by this {@link TargetSource}
41: */
42: Class getTargetClass();
43:
44: /**
45: * Will all calls to {@link #getTarget()} return the same object?
46: * <p>In that case, there will be no need to invoke
47: * {@link #releaseTarget(Object)}, and the AOP framework can cache
48: * the return value of {@link #getTarget()}.
49: * @return <code>true</code> if the target is immutable
50: * @see #getTarget
51: */
52: boolean isStatic();
53:
54: /**
55: * Return a target instance. Invoked immediately before the
56: * AOP framework calls the "target" of an AOP method invocation.
57: * @return the target object, which contains the joinpoint
58: * @throws Exception if the target object can't be resolved
59: */
60: Object getTarget() throws Exception;
61:
62: /**
63: * Release the given target object obtained from the
64: * {@link #getTarget()} method.
65: * @param target object obtained from a call to {@link #getTarget()}
66: * @throws Exception if the object can't be released
67: */
68: void releaseTarget(Object target) throws Exception;
69:
70: }
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