我想用Aspectj拦截所有java.sql.DataSource.getConnection方法,
我使用了这个切入点:
"execution(public java.sql.Connection javax.sql.DataSource+.getConnection(..))"
它工作正常。
但是我遇到一些类,例如org.apache.tomcat.jdbc.pool.DataSource,这些类在此切入点不起作用的类层次结构中实现,其中DataSource方法在未实现DataSource的层次结构中的类中,只有最顶级的类才实现DataSource:
class BaseDataSource {
public Connection getConnection() throws SQLException {
return null;
}
public Connection getConnection(String username, String password) throws SQLException {
return null;
}
implements all DataSource Methods...
}
class MyDataSource extends BaseDataSource implements java.sql.DataSource{
//does not implement DataSource methods
}
BaseDataSource不实现DataSource,但是具有所有DataSource方法的实现。
我发现唯一可行的切入点是:
execution(public java.sql.Connection *.getConnection(..)) && target(javax.sql.DataSource)
我的问题是,是否有更好的方法,而切入点是否可能对性能造成最坏的影响?
最佳答案
我在MCVE中复制了您的情况,如下所示:
基类实现DataSource
方法,但不实现接口:
package de.scrum_master.app;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.logging.Logger;
public class BaseClass {
public PrintWriter getLogWriter() throws SQLException { return null; }
public void setLogWriter(PrintWriter out) throws SQLException {}
public void setLoginTimeout(int seconds) throws SQLException {}
public int getLoginTimeout() throws SQLException { return 0; }
public Logger getParentLogger() throws SQLFeatureNotSupportedException { return null; }
public <T> T unwrap(Class<T> iface) throws SQLException { return null; }
public boolean isWrapperFor(Class<?> iface) throws SQLException { return false; }
public Connection getConnection() throws SQLException { return null; }
public Connection getConnection(String username, String password) throws SQLException { return null; }
}
子类实现接口
DataSource
,从基类继承方法:package de.scrum_master.app;
import javax.sql.DataSource;
public class SubClass extends BaseClass implements DataSource {}
驱动程序应用程序:
package de.scrum_master.app;
import java.sql.SQLException;
public class Application {
public static void main(String[] args) throws SQLException {
System.out.println("Aspect should not kick in");
new BaseClass().getConnection();
new BaseClass().getConnection("user", "pw");
System.out.println("Aspect should kick in");
new SubClass().getConnection();
new SubClass().getConnection("user", "pw");
}
}
方面:
此方面使用您当前正在使用的切入点。
package de.scrum_master.aspect;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
@Aspect
public class DataSourceConnectionAspect {
@Before("execution(public java.sql.Connection *.getConnection(..)) && target(javax.sql.DataSource)")
public void myAdvice(JoinPoint thisJoinPoint) {
System.out.println(thisJoinPoint);
}
}
控制台日志:
Aspect should not kick in
Aspect should kick in
execution(Connection de.scrum_master.app.BaseClass.getConnection())
execution(Connection de.scrum_master.app.BaseClass.getConnection(String, String))
毫不奇怪,一切都按预期进行。我认为这是一种有效的方法。当然,方面代码将编织到与
public java.sql.Connection *.getConnection(..))
匹配的每个方法中,并且会在运行时检查target(javax.sql.DataSource)
是否确实适用,另请参见javap
输出:Compiled from "BaseClass.java"
public class de.scrum_master.app.BaseClass {
(...)
public java.sql.Connection getConnection() throws java.sql.SQLException;
Code:
0: aload_0
1: instanceof #76 // class javax/sql/DataSource
4: ifeq 21
7: invokestatic #70 // Method de/scrum_master/aspect/DataSourceConnectionAspect.aspectOf:()Lde/scrum_master/aspect/DataSourceConnectionAspect;
10: getstatic #58 // Field ajc$tjp_0:Lorg/aspectj/lang/JoinPoint$StaticPart;
13: aload_0
14: aload_0
15: invokestatic #64 // Method org/aspectj/runtime/reflect/Factory.makeJP:(Lorg/aspectj/lang/JoinPoint$StaticPart;Ljava/lang/Object;Ljava/lang/Object;)Lorg/aspectj/lang/JoinPoint;
18: invokevirtual #74 // Method de/scrum_master/aspect/DataSourceConnectionAspect.myAdvice:(Lorg/aspectj/lang/JoinPoint;)V
21: aconst_null
22: areturn
public java.sql.Connection getConnection(java.lang.String, java.lang.String) throws java.sql.SQLException;
Code:
0: aload_1
1: astore 4
3: aload_2
4: astore 5
6: aload_0
7: instanceof #76 // class javax/sql/DataSource
10: ifeq 31
13: invokestatic #70 // Method de/scrum_master/aspect/DataSourceConnectionAspect.aspectOf:()Lde/scrum_master/aspect/DataSourceConnectionAspect;
16: getstatic #79 // Field ajc$tjp_1:Lorg/aspectj/lang/JoinPoint$StaticPart;
19: aload_0
20: aload_0
21: aload 4
23: aload 5
25: invokestatic #82 // Method org/aspectj/runtime/reflect/Factory.makeJP:(Lorg/aspectj/lang/JoinPoint$StaticPart;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Lorg/aspectj/lang/JoinPoint;
28: invokevirtual #74 // Method de/scrum_master/aspect/DataSourceConnectionAspect.myAdvice:(Lorg/aspectj/lang/JoinPoint;)V
31: aconst_null
32: areturn
(...)
}
即如果当前实例不是
DataSource
,则对于正在实现这些非常特殊的方法模式的类也将进行运行时检查。但这应该很少见。有一种涉及ITD(类型间声明)的替代方法:您可以使基类直接实现接口,然后返回使用更有效的原始切入点。在基于注释的语法中,这是这样的:
package de.scrum_master.aspect;
import javax.sql.DataSource;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.DeclareParents;
@Aspect
public class DataSourceConnectionAspect {
@DeclareParents("de.scrum_master.app.BaseClass")
private DataSource dataSource;
@Before("execution(public java.sql.Connection javax.sql.DataSource+.getConnection(..))")
public void myAdvice(JoinPoint thisJoinPoint) {
System.out.println(thisJoinPoint);
}
}
不幸的是,使用我曾经测试过的AspectJ版本,AspectJ编译器引发了异常。那可能是一个错误,我将在以后进行调查并向维护人员报告。更新:我为此问题创建了AspectJ bug ticket #550494。更新2:该错误已在AspectJ 1.9.5中修复。
但是,如果仅使用本机AspectJ语法,则可以使用。唯一的坏消息是,如果您使用javac + LTW并依靠AspectJ weaver在类加载期间完成方面,那么它将不再起作用。您必须使用AspectJ编译器ajc以本机语法编译方面。
package de.scrum_master.aspect;
import javax.sql.DataSource;
import de.scrum_master.app.BaseClass;
public aspect DataSourceConnectionAspect {
declare parents: BaseClass implements DataSource;
before() : execution(public java.sql.Connection javax.sql.DataSource+.getConnection(..)) {
System.out.println(thisJoinPoint);
}
}
现在,控制台日志更改为:
Aspect should not kick in
execution(Connection de.scrum_master.app.BaseClass.getConnection())
execution(Connection de.scrum_master.app.BaseClass.getConnection(String, String))
Aspect should kick in
execution(Connection de.scrum_master.app.BaseClass.getConnection())
execution(Connection de.scrum_master.app.BaseClass.getConnection(String, String))
当然,“方面不应该插入”在这里不再适用,因为现在我们确实希望它可以插入,因为
BaseClass
现在直接实现了DataSource
接口。免责声明:仅当所有接口方法确实存在于基类中时,此方法才有效(幸运的是
org.apache.tomcat.jdbc.pool.DataSourceProxy
就是这种情况),即,您可以相应地调整我的方面。如果基类仅实现部分预期的接口方法,则还可以通过本机语法通过ITD添加它们,但是我在这里不再赘述,我的回答已经很长了。最后但并非最不重要的是,新方法的字节码如下所示:
Compiled from "BaseClass.java"
public class de.scrum_master.app.BaseClass implements javax.sql.DataSource {
(...)
public java.sql.Connection getConnection() throws java.sql.SQLException;
Code:
0: getstatic #58 // Field ajc$tjp_0:Lorg/aspectj/lang/JoinPoint$StaticPart;
3: aload_0
4: aload_0
5: invokestatic #64 // Method org/aspectj/runtime/reflect/Factory.makeJP:(Lorg/aspectj/lang/JoinPoint$StaticPart;Ljava/lang/Object;Ljava/lang/Object;)Lorg/aspectj/lang/JoinPoint;
8: astore_1
9: invokestatic #70 // Method de/scrum_master/aspect/DataSourceConnectionAspect.aspectOf:()Lde/scrum_master/aspect/DataSourceConnectionAspect;
12: aload_1
13: invokevirtual #74 // Method de/scrum_master/aspect/DataSourceConnectionAspect.ajc$before$de_scrum_master_aspect_DataSourceConnectionAspect$1$19879111:(Lorg/aspectj/lang/JoinPoint;)V
16: aconst_null
17: areturn
public java.sql.Connection getConnection(java.lang.String, java.lang.String) throws java.sql.SQLException;
Code:
0: aload_1
1: astore 4
3: aload_2
4: astore 5
6: getstatic #77 // Field ajc$tjp_1:Lorg/aspectj/lang/JoinPoint$StaticPart;
9: aload_0
10: aload_0
11: aload 4
13: aload 5
15: invokestatic #80 // Method org/aspectj/runtime/reflect/Factory.makeJP:(Lorg/aspectj/lang/JoinPoint$StaticPart;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Lorg/aspectj/lang/JoinPoint;
18: astore_3
19: invokestatic #70 // Method de/scrum_master/aspect/DataSourceConnectionAspect.aspectOf:()Lde/scrum_master/aspect/DataSourceConnectionAspect;
22: aload_3
23: invokevirtual #74 // Method de/scrum_master/aspect/DataSourceConnectionAspect.ajc$before$de_scrum_master_aspect_DataSourceConnectionAspect$1$19879111:(Lorg/aspectj/lang/JoinPoint;)V
26: aconst_null
27: areturn
(...)
}
如果比较两个
javap
日志,您不仅会注意到现在它显示implements javax.sql.DataSource
,而且在旧版本中,这两种方法都有22/32字节码指令,而在新版本中,只有17 / 27。例如,在旧版本中,您看到instanceof #76 // class javax/sql/DataSource
。在新版本中,不再需要instanceof
检查。您可以自己决定是否值得使用ITD和本机语法。无论如何,我个人都使用本机语法和ajc,所以我会这样做。如果您以前从未使用过AspectJ编译器而仅使用LTW,则决定可能会有所不同。甚至是否会有可衡量的性能提升是另一个问题。我假设在涉及SQL数据库调用的场景中,可能不会影响到AspectJ的性能。 ;-)我只是想知道并回答您的问题。
更新:没有ITD的替代解决方案
根据您的评论,即使我认为这是一种干净优雅的解决方案,您也要避免使用ITD。但是,还有一种优化切入点匹配和性能的方法,如下所示:
package de.scrum_master.aspect;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
@Aspect
public class AlternativeSolutionAspect {
@Pointcut("execution(public java.sql.Connection getConnection(..))")
private static void getConnection() {}
@Pointcut("within(javax.sql.DataSource+)")
private static void withinDataSource() {}
@Pointcut("target(javax.sql.DataSource)")
private static void targetDataSource() {}
@Before("withinDataSource() && getConnection()")
public void interceptStatically(JoinPoint thisJoinPoint) {
System.out.println("[static] " + thisJoinPoint);
}
@Before("!withinDataSource() && getConnection() && targetDataSource()")
public void interceptDynamically(JoinPoint thisJoinPoint) {
System.out.println("[dynamic] " + thisJoinPoint);
}
}
说明:
建议
interceptStatically
负责查找“正常”情况下的所有方法执行,即实现接口和相应方法的(基类)。建议
interceptDynamically
负责(外部)休息,即在实际实例实现接口的地方执行方法,但方法是在未实现接口的(基)类中定义的。与您自己的纯动态解决方案的不同之处在于,在此我明确排除了可以静态确定的情况。现在,如果将我的
DataSourceConnectionAspect
与此AlternativeSolutionAspect
进行比较,那意味着什么?首先让我添加另一个示例类,以使其更清晰:package de.scrum_master.app;
import java.sql.Connection;
import java.sql.SQLException;
import javax.sql.DataSource;
public class SubClassOverridingMethods extends BaseClass implements DataSource {
@Override
public Connection getConnection() throws SQLException {
return super.getConnection();
// return null;
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return super.getConnection(username, password);
// return null;
}
}
现在,我们通过其他方法调用来扩展驱动程序应用程序:
package de.scrum_master.app;
import java.sql.SQLException;
public class Application {
public static void main(String[] args) throws SQLException {
System.out.println("Aspect should not kick in without ITD, but should with ITD");
new BaseClass().getConnection();
new BaseClass().getConnection("user", "pw");
System.out.println("Aspect should kick in");
new SubClass().getConnection();
new SubClass().getConnection("user", "pw");
System.out.println("Aspect should kick in");
new SubClassOverridingMethods().getConnection();
new SubClassOverridingMethods().getConnection("user", "pw");
}
}
其余的仍然像上面的示例一样。
DataSourceConnectionAspect
的控制台日志:Aspect should not kick in without ITD, but should with ITD
execution(Connection de.scrum_master.app.BaseClass.getConnection())
execution(Connection de.scrum_master.app.BaseClass.getConnection(String, String))
Aspect should kick in
execution(Connection de.scrum_master.app.BaseClass.getConnection())
execution(Connection de.scrum_master.app.BaseClass.getConnection(String, String))
Aspect should kick in
execution(Connection de.scrum_master.app.SubClassOverridingMethods.getConnection())
execution(Connection de.scrum_master.app.BaseClass.getConnection())
execution(Connection de.scrum_master.app.SubClassOverridingMethods.getConnection(String, String))
execution(Connection de.scrum_master.app.BaseClass.getConnection(String, String))
在情况3中,您会看到2行方法输出的4行日志输出,因为覆盖的方法调用
super.getConnection(..)
。如果他们只是在不使用超级调用的情况下做某事,则每个方法调用当然只有一条日志行。AlternativeSolutionAspect
的控制台日志:Aspect should not kick in without ITD, but should with ITD
Aspect should kick in
[dynamic] execution(Connection de.scrum_master.app.BaseClass.getConnection())
[dynamic] execution(Connection de.scrum_master.app.BaseClass.getConnection(String, String))
Aspect should kick in
[static] execution(Connection de.scrum_master.app.SubClassOverridingMethods.getConnection())
[dynamic] execution(Connection de.scrum_master.app.BaseClass.getConnection())
[static] execution(Connection de.scrum_master.app.SubClassOverridingMethods.getConnection(String, String))
[dynamic] execution(Connection de.scrum_master.app.BaseClass.getConnection(String, String))
因为我们在这里不使用ITD,所以情况1不会截获任何东西。情况2是动态截获的,而情况3中的静态方法可以是静态确定的,超级方法是动态确定的。同样,如果没有超级调用,情况3的每个方法调用将只有一行日志输出。
附注:如果您想知道,在超级呼叫的情况下,您自己的解决方案也会匹配两次。但是它会动态匹配两次,从而使其变慢。
关于java - 继承接口(interface)方法的aspectj切入点,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/57678474/