AOP in action. AspectJ (CTW) + Spring + LTW
I decided to implement AOP logging on the project and did not implement it. How and why, in fact, I want to share.
I will not describe the essence and principles of AOP, but I will describe only those problems that I encountered and whose solutions took a lot of time.
I had Spring, WebLogic, google.com and a project where I wanted to implement AOP logging. I have to say right before that I have never worked with AOP.
Spring AOP - uses proxy-based approach.
')
If we have a class (ClassA) with methods (methodA, methodB), then methodB () calls methodA () and an aspect (say after) that must be executed when calling methodA ():
And a certain class which, within the framework of some logic, makes the call of these methods:
The result of such a call (using the standard Spring AOP) will be:
And yet, the second time aspect does not work. The documentation is well described the principle of operation of Spring-AOP, after reading it, everything falls into place. This is the starting point.
Methods must be public. There are no comments here.
So, reading the documentation and other informative literature, I found the following solution:
Since I found good LTW documentation, I decided to use it. Price issue:
If you look at the example given in the documentation (aop.context):
Yes, everything works, but one BUT - we will rarely store our executable code and the aspect code directly in one class / package. This little detail they missed in the description. So, if we have a class (ClassA) and an aspect (AspectA) that are in different packages, then the following aop.xml will be a valid configuration:
In tag
The problem disappears immediately after turning off LTW.
What I made for myself and would like to add:
I will not describe the essence and principles of AOP, but I will describe only those problems that I encountered and whose solutions took a lot of time.
I had Spring, WebLogic, google.com and a project where I wanted to implement AOP logging. I have to say right before that I have never worked with AOP.
Problem number 1
Spring AOP - uses proxy-based approach.
')
If we have a class (ClassA) with methods (methodA, methodB), then methodB () calls methodA () and an aspect (say after) that must be executed when calling methodA ():
public class ClassA { public void methodA() { System.out.println("methodA"); } public void methodB() { System.out.println("methodB"); methodA(); } } public class AspectClass { public void aspectMethodA() { System.out.println("Aspect on method A"); } } And a certain class which, within the framework of some logic, makes the call of these methods:
public void execute() { // ..... classA.methodA(); classA.methodB(); // ..... } The result of such a call (using the standard Spring AOP) will be:
methodA Aspect on method A methodB methodA And yet, the second time aspect does not work. The documentation is well described the principle of operation of Spring-AOP, after reading it, everything falls into place. This is the starting point.
Problem number 2
Methods must be public. There are no comments here.
So, reading the documentation and other informative literature, I found the following solution:
- Load-time weaving (LTW).
- Compile-time weaving (CTW).
Since I found good LTW documentation, I decided to use it. Price issue:
- Now we don’t have a single .xml file where we nicely fold our pointcuts and aspects.
- We need to add a new aop.xml, where we have to specify our weavers (classes that are directly involved in the process), aspects.
- Pointcuts now appear directly above aspect.
@Before( "execution(* com.solutions. web.test.WebTestClass.testA())") public void testALog() {} - Above the aspect classes, the
@Aspectannotation@Aspect. - You need to add an argument when running JM / WebLogic:
-javaagent:${PATH_TO_LIB }/aspectjweaver.jar
Note
If you look at the example given in the documentation (aop.context):
<weaver> <include within="foo.*"/> </weaver> <aspects> <aspect name="foo.ProfilingAspect"/> </aspects> Yes, everything works, but one BUT - we will rarely store our executable code and the aspect code directly in one class / package. This little detail they missed in the description. So, if we have a class (ClassA) and an aspect (AspectA) that are in different packages, then the following aop.xml will be a valid configuration:
<weaver> <include within="com.example.ClassA"/> <!-- --> <include within="com.log.* "/> <!— > </weaver> <aspects> <aspect name="com.log.AspectA"/> </aspects> In tag
+ .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; + .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; + .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA;
+ .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; + .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA;
+ .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; + .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; -
+ .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; + .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; -
+ .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; + .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; -
+ .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; + .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA;
+ .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; + .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA;
+ .
â„– 3
LTW EAR/APP .
"As Costin said, there is unfortunately nothing we can do about this. Load-time weaving only works for specific deployment units such as WARs, and even there it is considered an advanced feature that won't work in all runtime environments.”
.
, CTW. :
- , aspect- pointcut-. C pointcut-, . ajc-, (ant, maven, gradle…).
â„– 4
CTW+LTW .
, LTW classpath TW :
java.lang.Exception: java.lang.NoSuchMethodError: com.aop.example.log.AspectA.aspectOf()Lcom/aop/example/log/AspectA; The problem disappears immediately after turning off LTW.
TOTAL
What I made for myself and would like to add:
- For all public top-level methods (EAR / APP, WEB level), you can use Spring AOP.
- For the entire level of non-public WEB and non-top-level methods, you can use LTW (if W is not used).
- For the entire APP level is not public and non-top level methods can be used CTW (if LTW is not used).
- In the tag of
app.context “weav” aspect-.
CTW and LTW are not compatible technologies.
Source: https://habr.com/ru/post/186940/
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