1 | /* |
2 | * Copyright 2006-2007 the original author or authors. |
3 | * |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
5 | * you may not use this file except in compliance with the License. |
6 | * You may obtain a copy of the License at |
7 | * |
8 | * http://www.apache.org/licenses/LICENSE-2.0 |
9 | * |
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.batch.repeat.interceptor; |
18 | |
19 | import org.aopalliance.intercept.MethodInterceptor; |
20 | import org.aopalliance.intercept.MethodInvocation; |
21 | import org.springframework.aop.ProxyMethodInvocation; |
22 | import org.springframework.batch.repeat.ExitStatus; |
23 | import org.springframework.batch.repeat.RepeatCallback; |
24 | import org.springframework.batch.repeat.RepeatContext; |
25 | import org.springframework.batch.repeat.RepeatException; |
26 | import org.springframework.batch.repeat.RepeatOperations; |
27 | import org.springframework.batch.repeat.support.RepeatTemplate; |
28 | import org.springframework.util.Assert; |
29 | |
30 | /** |
31 | * A {@link MethodInterceptor} that can be used to automatically repeat calls to |
32 | * a method on a service. The injected {@link RepeatOperations} is used to |
33 | * control the completion of the loop. Independent of the completion policy in |
34 | * the {@link RepeatOperations} the loop will repeat until the target method |
35 | * returns null or false. Be careful when injecting a bespoke |
36 | * {@link RepeatOperations} that the loop will actually terminate, because the |
37 | * default policy for a vanilla {@link RepeatTemplate} will never complete if |
38 | * the return type of the target method is void (the value returned is always |
39 | * not-null, representing the {@link Void#TYPE}). |
40 | * |
41 | * @author Dave Syer |
42 | */ |
43 | public class RepeatOperationsInterceptor implements MethodInterceptor { |
44 | |
45 | private RepeatOperations repeatOperations = new RepeatTemplate(); |
46 | |
47 | /** |
48 | * Setter for the {@link RepeatOperations}. |
49 | * |
50 | * @param batchTempate |
51 | * @throws IllegalArgumentException if the argument is null. |
52 | */ |
53 | public void setRepeatOperations(RepeatOperations batchTempate) { |
54 | Assert.notNull(batchTempate, "'repeatOperations' cannot be null."); |
55 | this.repeatOperations = batchTempate; |
56 | } |
57 | |
58 | /** |
59 | * Invoke the proceeding method call repeatedly, according to the properties |
60 | * of the injected {@link RepeatOperations}. |
61 | * |
62 | * @see org.aopalliance.intercept.MethodInterceptor#invoke(org.aopalliance.intercept.MethodInvocation) |
63 | */ |
64 | public Object invoke(final MethodInvocation invocation) throws Throwable { |
65 | |
66 | final ResultHolder result = new ResultHolder(); |
67 | // Cache void return value if intercepted method returns void |
68 | final boolean voidReturnType = Void.TYPE.equals(invocation.getMethod().getReturnType()); |
69 | if (voidReturnType) { |
70 | // This will be ignored anyway, but we want it to be non-null for |
71 | // convenience of checking that there is a result. |
72 | result.setValue(new Object()); |
73 | } |
74 | |
75 | try { |
76 | repeatOperations.iterate(new RepeatCallback() { |
77 | |
78 | public ExitStatus doInIteration(RepeatContext context) throws Exception { |
79 | try { |
80 | |
81 | MethodInvocation clone = invocation; |
82 | if (invocation instanceof ProxyMethodInvocation) { |
83 | clone = ((ProxyMethodInvocation) invocation).invocableClone(); |
84 | } |
85 | else { |
86 | throw new IllegalStateException( |
87 | "MethodInvocation of the wrong type detected - this should not happen with Spring AOP, so please raise an issue if you see this exception"); |
88 | } |
89 | |
90 | Object value = clone.proceed(); |
91 | if (voidReturnType) { |
92 | return ExitStatus.CONTINUABLE; |
93 | } |
94 | if (!isComplete(value)) { |
95 | // Save the last result |
96 | result.setValue(value); |
97 | return ExitStatus.CONTINUABLE; |
98 | } |
99 | else { |
100 | result.setFinalValue(value); |
101 | return ExitStatus.FINISHED; |
102 | } |
103 | } |
104 | catch (Throwable e) { |
105 | if (e instanceof Exception) { |
106 | throw (Exception) e; |
107 | } |
108 | else { |
109 | throw new RepeatOperationsInterceptorException("Unexpected error in batch interceptor", e); |
110 | } |
111 | } |
112 | } |
113 | |
114 | }); |
115 | } |
116 | catch (Throwable t) { |
117 | // The repeat exception should be unwrapped by the template |
118 | throw t; |
119 | } |
120 | |
121 | if (result.isReady()) { |
122 | return result.getValue(); |
123 | } |
124 | |
125 | // No result means something weird happened |
126 | throw new IllegalStateException("No result available for attempted repeat call to " + invocation |
127 | + ". The invocation was never called, so maybe there is a problem with the completion policy?"); |
128 | } |
129 | |
130 | /** |
131 | * @param result |
132 | * @return |
133 | */ |
134 | private boolean isComplete(Object result) { |
135 | return result == null || (result instanceof Boolean) && !((Boolean) result).booleanValue(); |
136 | } |
137 | |
138 | /** |
139 | * Simple wrapper exception class to enable nasty errors to be passed out of |
140 | * the scope of the repeat operations and handled by the caller. |
141 | * |
142 | * @author Dave Syer |
143 | * |
144 | */ |
145 | private static class RepeatOperationsInterceptorException extends RepeatException { |
146 | /** |
147 | * @param message |
148 | * @param e |
149 | */ |
150 | public RepeatOperationsInterceptorException(String message, Throwable e) { |
151 | super(message, e); |
152 | } |
153 | } |
154 | |
155 | /** |
156 | * Simple wrapper object for the result from a method invocation. |
157 | * |
158 | * @author Dave Syer |
159 | * |
160 | */ |
161 | private static class ResultHolder { |
162 | private Object value = null; |
163 | |
164 | private boolean ready = false; |
165 | |
166 | /** |
167 | * Public setter for the Object. |
168 | * @param value the value to set |
169 | */ |
170 | public void setValue(Object value) { |
171 | this.ready = true; |
172 | this.value = value; |
173 | } |
174 | |
175 | /** |
176 | * @param value |
177 | */ |
178 | public void setFinalValue(Object value) { |
179 | if (ready) { |
180 | // Only set the value the last time if the last time was also |
181 | // the first time |
182 | return; |
183 | } |
184 | setValue(value); |
185 | } |
186 | |
187 | /** |
188 | * Public getter for the Object. |
189 | * @return the value |
190 | */ |
191 | public Object getValue() { |
192 | return value; |
193 | } |
194 | |
195 | /** |
196 | * @return true if a value has been set |
197 | */ |
198 | public boolean isReady() { |
199 | return ready; |
200 | } |
201 | } |
202 | |
203 | } |