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An Overview of S2AOPThe main idea of AOPAdvice(MethodInterceptor)Advice is a block of codes which will be inserted into another program. This could be called Interceptor. Joinpoint(MethodInvocation)Joinpoint is a point which Advice will be associated with a targeted class. Advice is allowed to get information about a method name and arguments from Joinpoint. PointcutPointcut is used to define the point where Jopinpoint is set in. AspectAspect associates Advice with Pointcut. InterTypeInterType modifies class internal structures, including adding fields, methodds and interfaces. AOP advantates
S2AOP advantages
What you have to care about S2AOP
Brief Notes of S2AOPThe file you needYou need a configuration file (known as "dicon file") for S2Container to use S2AOP. However, you can place a configuration file in any directory, a configuration file is commonly created in the same directory(a.k.a. folder) as the "Crosscutting Concern" or the targeted component resides. Setup file DescriptionsAspect Tag (mandatory for AOP)An aspect tag is used to associate an aspect with a component. Write the Interceptor configuration in the body by using the OGNL expression or in the nested tag accompanied by the component tag. Pay attentionThe component specified by the aspect tag will be get through the container while its initialization processes are going on. This indicates that a new instance doesn't create everytime when an Interceptor method is invoked under the condition that an instance attribute of a component is assigned as a prototype. pointcut attribute(optional)You can specify multiple method names delimited by commmas. If you don't set any pointcut, all implemented methods in a component will be invoked. You can use the regular expression(JDK1.4 regex) to specify method names. Configuration ExampleSuppose you want to set the aspect in both getTime() method and hasCode() method of java.util.Date class by means of a pointcut attribute, then the configuration will be as follows.
<component class="java.util.Date">
<aspect pointcut="getTime,hashCode">
<component class="org.seasar.framework.aop.interceptors.TraceInterceptor"/>
</aspect>
</component>
The example shown below describes how to use regular expression to set an aspect.
<component class="java.util.Date">
<aspect pointcut=".*">
<component class="org.seasar.framework.aop.interceptors.TraceInterceptor"/>
</aspect>
</component>
interType TagSpecifies interType which is added into components. Either OGNL expressions in the body or the child component tag is used for the value passed as an interType. Configuration Example
<component class="java.util.Date">
<interType>
<component class="org.seasar.framework.aop.intertype.PropertyInterType"/>
</interType>
</component>
Available S2AOP InterceptorsFollowing Interceptors are provided by S2AOP. Besides, you can define your own Interceptor easily. (1) TraceInterceptorClass Nameorg.seasar.framework.aop.interceptors.TraceInterceptor DescriptionThis Interceptor handles a trace as a "Crosscutting Concern". Dicon file shown below is an example that TraceInterceptor is applied to getTime() method of java.uitl.Date class.
<component class="java.util.Date">
<aspect pointcut="getTime">
<component class="org.seasar.framework.aop.interceptors.TraceInterceptor"/>
</aspect>
</component>
Please read TraceInterceptor for further information. (2) ThrowsInterceptorClass Nameorg.seasar.framework.aop.interceptors.ThrowsInterceptor DescriptionThis Interceptor handles an exception as a "Crosscutting Concern". Implement the method "Object handleThrowable(Throwable, MethodInvocation)" in your class inherited from ThrowsInterceptor before you use this. You can assign a subclass of java.lang.Throwable to the first parameter of this method. If you define the method "Object handleThrowable(IOException, MethodInvocation)", the exception will be caught by the object which type is IOException or the subclass of IOException when the excpetion raised in the component associated with ThrowsInterceptor. You are allowed to define multiple handleThrowable() methods. Please read ThrowsInterceptor for further information. (3) ToStringInterceptorClass Nameorg.seasar.framework.aop.interceptors.ToStringInterceptor DescriptionToStringInterceptor treats the string processing by the toString() method as "Crosscutting Concern".
<component class="java.util.Date">
<aspect pointcut="toString">
<component class="org.seasar.framework.aop.interceptors.ToStringInterceptor"/>
</aspect>
</component>
Please refer to the ToStringInterceptor sample in details. (4) MockInterceptorClass Nameorg.seasar.framework.aop.interceptors.MockInterceptor DescriptionThis Interceptor let a test made by Mock easier. Please read Testing for further information. (5) DelegateInterceptorClass Nameorg.seasar.framework.aop.interceptors.DelegateInterceptor DescriptionThis Interceptor delegates a method invocation to another component. A delegation is performed when a component is assigned to a target property of DelegateInterceptor. If you want to specify a method name explicitly to support different method names, use "DelegateInterceptor#addMethodNameMap(String methodName, String targetMethodName)". Suppose you want to let the method bar() be delegated to foo.bar2(), then your code might be like this: "DelegateInterceptor#setTarget(foo), DelegateInterceptor#addMethodNameMap("bar", "bar2")". Please read DelegateInterceptor for further information. Pay attentionA component assigned to a target property will be get through the container while its initialization processes are going on. As a result, the same instance will be used even if the instance attribute of the component is a property. If you want to get a new instance for every method invocation, use PrototypeDelegateInterceptor described below. (6) PrototypeDelegateInterceptorClass Nameorg.seasar.framework.aop.interceptors.PrototypeDelegateInterceptor DescriptionThis Interceptor delegates a method invocation to another component. A new component will be get from a container in every method invocation. The delegation is performed when the targeted component name is assigned to the targetName property of PrototypeDelegateInterceptor. If you want to set a method name explicitly to support different method names, use "PrototypeDelegateInterceptor#setTarget(foo), PrototypeDelegateInterceptor#addMethodNameMap("bar", "bar2")". Please read PrototypeDelegateInterceptor for further information. (7) SyncInterceptorClass Nameorg.seasar.framework.aop.interceptors.SyncInterceptor DescriptionThis Interceptor synchronizes a multiple method invocations by an aspect. You don't need to modify your code when you want to sychronize method invocations. Please read SyncInterceptor for further information. (8) InterceptorChainClass Nameorg.seasar.framework.aop.interceptors.InterceptorChain DescriptionThis Interceptor enables you to combine multiple Interceptors and to reuse them easily. If you want to adopt a combination to more than one component, give the name of InterceptorChain into each component as follows. <component name="interceptor1" .../> <component name="interceptor2" .../> <component name="interceptor3" .../> (9) InterceptorLifecycleAdapterClass Nameorg.seasar.framework.aop.interceptors.InterceptorLifecycleAdapter DescriptionInterceptor instances are built into classes only when initializeing container. This is why new interceptors are not built into classes even if instance property is prototype. In this case, applies InterceptorLifecycleAdapter to MethodInterceptor#invoke().
<component name="myInterceptor" instance="prototype" .../>
<aspect pointcut="invoke">
<component class="org.seasar.framework.aop.interceptors.InterceptorLifecycleAdapter">
</aspect>
</component>
<component ...>
<aspect>myInterceptor</aspect>
</component>
How to define your own InterceptorDescriptionTo define your own Interceptor, you need to implement an interface or an abstract class shown below.
The invoke() method shown below is the only one that you have to implement in both cases.
AbstractInterceptor is an abstract class and implements MethodInterceptor. AbstracInterceptor has two methods, createProxy() and getTargetClass() shown below. createProxy() method is used to get a Proxy object. getTargetClass() method is used to get a target class which an aspect is associated. When Interceptor requires a name of a class that an aspect is associated with, for example, logging Interceptor, you can get a required class name easily from AbstractInterceptor.
You can get a target object, method and arguments from MethodInvocation object given as a parameter of getTargetClass() method. getThis() method has a feature to get a class name from a bytecode. proceed() method invokes a concrete method and gets the result through this invocation. Following is an example how to use proceed() method. WarningInterceptor instances are built into classes only when initializeing container. This is why new interceptors are not built into classes even if instance property is prototype. Example
public class ABS implements MethodInterceptor {
public Object invoke(MethodInvocation invocation) throws Throwable {
System.out.println("Before");
Object ret = invocation/proceed();
System.out.println("After");
return ret;
}
}
This example consists of two parts, before and after the proceed() method. The first part is ensured to be executed before proceed() method and the second part is ensured to be done after proceed() method. Suppose multiple aspects associated with only one component, then aspects will be invoked as follows:
Please read How to define your own Interceptor for further information. Available S2AOP InterTypesFollowing Intertypes are provided by S2AOP. Besides, you can define your own InterType easily. (1) PropertyTraceInterTypeClass Nameorg.seasar.framework.aop.intertype.PropertyInterType DescriptionPropertyInterType creates the setter and getter method for the field. WarningPropertyInterType doesn't create the getter and setter method for the private field. We need to define field scope as either protected or package.
<component class="Hoge">
<interType>
<component class="org.seasar.framework.aop.interType.PropertyInterType"/>
</interType>
</component>
We can specify the Property annotation for the fields where we want to create the getter and setter method.
import org.seasar.framework.container.annotation.tiger.Property;
import org.seasar.framework.container.annotation.tiger.PropertyType;
public class Hoge {
@Property
int foo;
@Property(PropertyType.READ)
long bar;
@Property(PropertyType.WRITE)
String baz;
}
Backport175 annotation is as follows.
public class Hoge {
/** @org.seasar.framework.container.annotation.backport175.Property */
int foo;
/** @org.seasar.framework.container.annotation.backport175.Property("read") */
long bar;
/** @org.seasar.framework.container.annotation.backport175.Property("write") */
String baz;
}
In the above sample, We create the getter and setter method in foo field, and create the getter method in bar field, and create the setter method in baz field. We can sepecify the Property annotation for a class. The annotation for a class is adapted for the fields which we don't specify the annotation.
import org.seasar.framework.container.annotation.tiger.Property;
import org.seasar.framework.container.annotation.tiger.PropertyType;
@Property
public class Hoge {
int foo;
long bar;
@Property(PropertyType.NONE)
String baz;
}
Backport175 annotation is as follows.
/** @org.seasar.framework.container.annotation.backport175.Property */
public class Hoge {
int foo;
long bar;
/** @org.seasar.framework.container.annotation.backport175.Property("none") */
String baz;
}
In the above sample, we create the getter and setter method in the foo and bar field, and don't create any method in the baz field. (2) InterTypeChainClass Nameorg.seasar.framework.aop.intertye.InterTypeChain DescriptionInterType enables you to combine multiple InterTypes and to reuse them easily. <component name="interType1" .../> <component name="interType2" .../> <component name="interType3" .../> How to define your own InterTypeDescriptionTo define your own InterType, you need to implement an interface or an abstract class shown below.
The class implementing InterType need to implement the folloing method.
InterType is applied to targetClass and is built into enhancedClass. Please refer to Javassist, Tutorial, JavaDoc for details. AbstractInterType is an abstract class implementing InterType. The sub-class of InterType need to implement folloing methods.
AbstractInterType acquires objects using folloing methods.
AbstractInterType supplies following utility methods for adding fields, methods, and interfaces.
AOP without "dicon file"This section describes how to put aspects into your program without dicon file. Four solutions shown below are provided.
This is an example how to insert an aspect without dicon file. This example adopts TraceInterceptor to java.uitl.Date, and let getTime() method be a target method.
Pointcut pointcut = new PointcutImpl(new String[]{"getTime"});
Aspect aspect = new AspectImpl(new TraceInterceptor(), pointcut);
AopProxy aopProxy = new AopProxy(Date.class, new Aspect[]{aspect});
Date proxy = (Date) aopProxy.create();
proxy.getTime();
ExampleYou have to finish a setup before running these samples. TraceInterceptorFirst example uses TraceInterceptor. This shows you how to output a trace when getTime() and hasCode() methods in both java.util.Array and java.util.Date classes are invoked. Write two files explained below.
How to write dicon file
Trace.dicon
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components>
<component name="traceInterceptor"
class="org.seasar.framework.aop.interceptors.TraceInterceptor"/>
<component class="java.util.ArrayList>
<aspect>traceInterceptor</aspect>
</component>
<component class="java.util.Date">
<arg>0</arg>
<aspect pointcut="getTime, hashCode">
traceInterceptor
</aspect>
</component>
</components>
How to write a cline Java program
AopTraceClient.java
package examples.aop.traceinterceptor;
import java.util.Date;
import java.util.List;
import org.seasar.framework.container.S2Container;
import org.seasar.framework.container.factory.S2ContainerFactory;
public class AopTraceClient {
private static String PATH = "examples/aop/traceinterceptor/Trace.dicon";
public static void main(String[] args) {
S2Container container = S2ContainerFactory.create(PATH);
ArrayList list = (List) container.getComponent(ArrayList.class);
list.size();
Date date = (Date) container.getComponent(Date.class);
date.getTime();
date.hashCode();
}
}
Output You see an output shown below. This means that the traces are outputed both before and after the method invocation. As for Date component, you know java.util.Date#getTime() method is traced between BEGIN and END of hasCode() method, too. The reason is that getTime() method is used in hashCode() method. BEGIN java.util.ArrayList#size() END java.util.ArrayList#size() : 0 BEGIN java.util.Date#getTime() END java.util.Date#getTime() : 0 BEGIN java.util.Date#hashCode() BEGIN java.util.Date#getTime() END java.util.Date#getTime() : 0 END java.util.Date#hashCode() : 0 This example is included in the directory, seasar2/src/examples/aop/traceinterceptor. ThrowsInterceptor(1)The second example uses ThrowsInterceptor. This shows you how to go processing through to the end even if an exception occurs. Write four files explained below.
How to define a class that throws exception
Checker.java
package examples.aop.throwsinterceptor;
public class Checker {
public void check(String str) {
if (str != null) {
System.out.println(str);
} else {
throw new NullPointerException("null");
}
}
}
How to define Interceptor inherited from ThrowsInterceptor
HandleThrowableInterceptor.java
package examples.aop.throwsinterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.seasar.framework.aop.interceptors.ThrowsInterceptor;
public class HandleThrowableInterceptor extends ThrowsInterceptor {
public void handleThrowable(Throwable t, MethodInvocation invocation)
throws Throwable {
}
}
How to write dicon file
Checker.dicon
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components>
<component name="handleThrowableInterceptor"
class="examples.aop.throwsinterceptor.HandleThrowableInterceptor"/>
<component class="examples.aop.throwsinterceptor.Checker">
<aspect pointcut="check">
handleThrowableInterceptor
</aspect>
</component>
</components>
How to write a client Java class
AopCheckerClient.java
package examples.aop.throwsinterceptor;
import org.seasar.framework.container.S2Container;
import org.seasar.framework.container.factory.S2ContainerFactory;
public class AopCheckerClient {
private static String PATH = "examples/aop/throwsinterceptor/Checker.dicon";
public static void main(String[] args) {
S2Container container = S2ContainerFactory.create(PATH);
Checker checker = (Checker) container.getComponent(Checker.class);
checker.check("foo");
checker.check(null);
checker.check("hoge");
}
}
Output You see the string "hoge", so you know that the raised exception didn't stop processing. foo hoge This example is included in seasar2/src/examples/aop/throwsinterceptor (2) This ThrowsInterceptor example shows you how to replace the type of exeception with another Interceptor. Modify HandleThrowableInterceptor defined above. How to make Interceptor to throw a new exception Suppose org.seasar.framework.exception.SRuntimeException will be thrown when the first argument of handleThrowable(Throwable, MethodInvocation) method is NullPointerException, then you need to modify HandleThrowableInterceptor as follows.
package examples.aop.throwsinterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.seasar.framework.aop.interceptors.ThrowsInterceptor;
import org.seasar.framework.exception.SRuntimeException;
public class HandleThrowableInterceptor extends ThrowsInterceptor {
public void handleThrowable(NullPointerException t, MethodInvocation invocation)
throws Throwable {
throw new SRuntimeException("ESSR0007", new Object[] { "argument" });
}
}
You use other three files, Checker.java, Checker.dicon and AopCheckerClient.java, to run this example. OutputYou see new error messages shown below.
foo
Exception in thread "main" org.seasar.framework.exception.SRuntimeException:
[ESSR0007]argument should not be null or empty
at examples.aop.throwsinterceptor.HandleThrowableInterceptor.handleThrowable(
HandleThrowableInterceptor.java:12)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(
DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.seasar.framework.aop.interceptors.ThrowsInterceptor.invoke(
ThrowsInterceptor.java:54)
at examples.aop.throwsinterceptor.Checker$$EnhancedByS2AOP$$16672d6$$
MethodInvocation$$check0.proceed(MethodInvocationClassGenerator.java)
at examples.aop.throwsinterceptor.Checker$$EnhancedByS2AOP$$16672d6.check(
Checker$$EnhancedByS2AOP$$16672d6.java)
at examples.aop.throwsinterceptor.AopCheckerClient.main(AopCheckerClient.java:13)
This example is included in seasar2/src/examples/aop/throwsinterceptor ToStringInterceptorWe can automatically output the fields information using ToStringInterceptor. The written files are as follows.
Creation entity classes Entity.java
package examples.aop.tostringinterceptor;
import java.util.HashMap;
import java.util.Map;
public class Entity {
private int intValue = 1;
private static int staticIntValue = 12;
private double doubleValue = 12.3;
private String stringValue = "1234";
public static final int staticFinalIntValue = 12345;
private Map mapValue = new HashMap();
private InnerEntity innerEntity;
public Entity(InnerEntity innerEntity) {
this.innerEntity = innerEntity;
}
}
EntityImpl.java
package examples.aop.tostringinterceptor;
public class EntityImpl extends Entity {
private int implValue = 1;
public EntityImpl(InnerEntity innerEntity) {
super(innerEntity);
}
}
EntityImplImpl.java
package examples.aop.tostringinterceptor;
public class EntityImplImpl extends EntityImpl {
private int implImplValue = 1;
public EntityImplImpl(InnerEntity innerEntity) {
super(innerEntity);
}
}
InnerEntity.java
package examples.aop.tostringinterceptor;
public class InnerEntity {
int innerInt = 0;
long innerLong = 234;
String str = "foo";
char[] charArray = new char[]{'a', 'b', 'c'};
}
How to write dicon file
ToString.dicon
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components>
<component name="toStringInterceptor"
class="org.seasar.framework.aop.interceptors.ToStringInterceptor"/>
<component class="examples.aop.tostringinterceptor.EntityImplImpl">
<arg>
innterEntity
</arg>
<aspect pointcut="toString">
toStringInterceptor
</aspect>
</component>
<component name="innterEntity"
class="examples.aop.tostringinterceptor.InnerEntity">
<aspect pointcut="toString">
toStringInterceptor
</aspect>
</component>
</components>
Creation the main program
AopTraceClient.java
package examples.aop.tostringinterceptor;
import org.seasar.framework.container.S2Container;
import org.seasar.framework.container.factory.S2ContainerFactory;
public class AopToStringClient {
private static String PATH = "examples/aop/tostringinterceptor/ToString.dicon";
public static void main(String[] args) {
S2Container container = S2ContainerFactory.create(PATH);
Entity entity = (Entity) container.getComponent(EntityImpl.class);
System.out.println(entity);
}
}
Output
examples.aop.tostringinterceptor.EntityImplImpl@1db4f6f[
implImplValue=3,implValue=2,intValue=1,staticIntValue=12,doubleValue=12.3,
stringValue="1234",staticFinalIntValue=12345,mapValue={},
innerEntity=examples.aop.tostringinterceptor.InnerEntity@13c1b02[
innerInt=0,innerLong=234,str="foo",charArray={'a','b','c'}]]
This example is included in seasar2/src/examples/aop/tostringinterceptor. DelegateInterceptorThe third example uses DelegateInterceptor of S2AOP. This shows how to delegate a method invocation to another class's method invocation.
An interface, IBase.java
IBase.java
package examples.aop.delegateinterceptor;
public interface IBase {
public abstract void run();
}
An abstract class, Dummy.java
Dummy.java
package examples.aop.delegateinterceptor;
public abstract class Dummy implements IBase {
}
A concrete class, Substance.java
Substance.java
package examples.aop.delegateinterceptor;
public class Substance implements IBase {
public void run() {
System.out.println("substance");
}
}
Dicon file
Delegate.dicon
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components>
<component class="sample.aop.delegateinterceptor.Dummy">
<aspect>
<component
class="org.seasar.framework.aop.interceptors.DelegateInterceptor">
<initMethod name="setTarget">
<arg>new sample.aop.delegateinterceptor.Substance()</arg>
</initMethod>
</component>
</aspect>
</component>
</components>
A client Java class
package examples.aop.delegateinterceptor;
import org.seasar.framework.container.S2Container;
import org.seasar.framework.container.factory.S2ContainerFactory;
public class AopDelegateClient {
private static String PATH = "examples/aop/delegateinterceptor/Delegate.dicon";
public static void main( String[] args ){
S2Container container = S2ContainerFactory.create(PATH);
IBase base = (IBase) container.getComponent(Dummy.class);
base.run();
}
}
Output The output string "substance" will appear on a console, so you can check that Dummy#run() has been delegated to Substance#run() substance This example is included in seasar2/src/examples/aop/delegateinterceptor. PrototypeDelegateInterceptorThis example uses PrototypeDelegateInterceptor and delegates from a singlton component to a prototype component.
An interface, IBase.java
IBase.java
package examples.aop.delegateinterceptor;
public interface IBase {
public abstract void run();
}
An abstract class that implements the interface, Dummy.java
Dummy.java
package examples.aop.delegateinterceptor;
public abstract class Dummy implements IBase {
}
A concrete class that implements the interface, Substance.java
Substance.java
package examples.aop.delegateinterceptor;
public class Substance implements IBase {
public void run() {
System.out.println(this);
}
}
Dicon file
PrototypeDelegate.dicon
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components>
<component class="sample.aop.delegateinterceptor.Dummy">
<aspect>
<component
class="org.seasar.framework.aop.interceptors.PrototypeDelegateInterceptor">
<property name="targetName">"target"</property>
</component>
</aspect>
</component>
<component name="target"
class="examples.aop.prototypedelegateinterceptor.Substance"
instance="prototype"/>
</components>
A client Java class
package examples.aop.prototypedelegateinterceptor;
import org.seasar.framework.container.S2Container;
import org.seasar.framework.container.factory.S2ContainerFactory;
public class AopDelegateClient {
private static String PATH =
"examples/aop/prototypedelegateinterceptor/PrototypeDelegate.dicon";
public static void main( String[] args ){
S2Container container = S2ContainerFactory.create(PATH);
IBase base = (IBase) container.getComponent(Dummy.class);
for (int i = 0; i < 5; ++i) {
base.run();
}
}
}
Output The output strings such as "examples.aop.prototypedelegateinterceptor.Substance@xxxxxx" will appear on a console, so you can check that Dummy#run() has been delegated to Substance#run(). Besides, you know that new Substance instances are created in every run() method invocation because output strings contain "@" followed by a hashcode value. examples.aop.prototypedelegateinterceptor.Substance@ae533a examples.aop.prototypedelegateinterceptor.Substance@da18ac examples.aop.prototypedelegateinterceptor.Substance@8a0544 examples.aop.prototypedelegateinterceptor.Substance@401369 examples.aop.prototypedelegateinterceptor.Substance@e49dcd This example is included in seasar2/src/examples/aop/delegateinterceptor SyncInterceptorThis example uses SyncInterceptor to be able to synchronize accessing to one object from multiple threads.
Count.java
package examples.aop.syncinterceptor;
public interface Count {
public void add();
public int get();
}
A concrete class, CountImple.java
CountImpl.java
package examples.aop.syncinterceptor;
public class CountImpl implements Count {
private int _count = 0;
public void add() {
int a = _count;
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
_count = a + 1;
System.out.println(a);
}
public int get() {
return _count;
}
}
Dicon file
SyncCalc.dicon
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components>
<component class="examples.aop.syncinterceptor.CountImpl">
</component>
</components>
A client Java class
AopSyncClient.java
package examples.aop.syncinterceptor;
import org.seasar.framework.container.S2Container;
import org.seasar.framework.container.factory.S2ContainerFactory;
public class AopSyncClient {
private String PATH = "examples/aop/syncinterceptor/SyncCalc.dicon";
private Count _count = null;
public void init() {
S2Container container = S2ContainerFactory.create(PATH);
_count = (Count) container.getComponent(Count.class);
}
public void start() {
System.out.println("count: " + _count.get());
Runnable r = new Runnable() {
public void run() {
_count.add();
}
};
Thread[] thres = new Thread[5];
for (int i=0; i<5; i++) {
thres[i] = new Thread(r);
thres[i].start();
}
for (int i=0; i<5; i++) {
try {
thres[i].join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("count: " + _count.get());
}
public static void main(String[] args) {
AopSyncClient asc = new AopSyncClient();
asc.init();
asc.start();
}
}
Output This output shows that created threads aren't synchronized. count: 0 0 0 0 0 0 count: 1Next, redefine dicon file to make created threads to synchronize by SyncInterceptor.
SyncCalc.dicon
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components>
<component class="examples.aop.syncinterceptor.CountImpl">
<aspect>
<component class="org.seasar.framework.aop.interceptors.SyncInterceptor"/>
</aspect>
</component>
</components>
Output This output shows that all created threads are synchronized because counter value increases one by one. count: 0 0 1 2 3 4 count: 5 This example is included in seasar2/src/examples/aop/syncinterceptor How to define your own InterceptorThis section describes how you can make your own Interceptor. To help you to understand well, we adopt one example that get a target class name, method name and arguments. Besides, this example measures processing times needed in each method invocations. Also, we try to keep track a processing time that extremly consumes cpu power by our Interceptor. Write four files shown below.
How to define your own Intercepter
MeasurementInterceptor.java
package examples.aop.originalinterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.seasar.framework.aop.interceptors.AbstractInterceptor;
public class MeasurementInterceptor extends AbstractInterceptor{
public Object invoke(MethodInvocation invocation) throws Throwable {
long start = 0;
long end = 0;
StringBuffer buf = new StringBuffer(100);
buf.append(getTargetClass(invocation).getName());
buf.append("#");
buf.append(invocation.getMethod().getName());
buf.append("(");
Object[] args = invocation.getArguments();
if (args != null && args.length > 0) {
for (int i = 0; i < args.length; ++i) {
buf.append(args[i]);
buf.append(", ");
}
buf.setLength(buf.length() - 2);
}
buf.append(")");
try {
start = System.currentTimeMillis();
Object ret = invocation.proceed();
end = System.currentTimeMillis();
buf.append(" : ");
return ret;
} catch (Throwable t) {
buf.append(" Throwable:");
buf.append(t);
throw t;
} finally {
System.out.println(buf.toString() + (end - start));
}
}
}
How to wrtie a class that will be associated with Interceptor
HeavyProcess.java
package examples.aop.originalinterceptor;
public class HeavyProcess {
public void heavy(){
try{
Thread.sleep(5000);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
Dicon file
Measurement.dicon
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components>
<component name="measurement"
class="examples.aop.originalinterceptor.MeasurementInterceptor"/>
<component class="examples.aop.originalinterceptor.HeavyProcess">
<aspect pointcut="heavy">
measurement
</aspect>
</component>
</components>
A client Java class
AopMeasurementClient.java
package examples.aop.originalinterceptor;
import org.seasar.framework.container.S2Container;
import org.seasar.framework.container.factory.S2ContainerFactory;
public class AopMeasurementClient {
private static String PATH = "examples/aop/originalinterceptor/Measurement.dicon";
public static void main(String[] args) {
S2Container container = S2ContainerFactory.create(PATH);
HeavyProcess heavyProcess = (HeavyProcess) container
.getComponent(HeavyProcess.class);
heavyProcess.heavy();
}
}
Output You see the message shown below, so you know this class keeps track a class name, a method name, arguments and processing time. examples.aop.HeavyProcess#heavy() : 5004 This example is included in seasar2/src/examples/aop/originalinterceptor |
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