在Java中是否可以设置在创建任何对象时调用的默认侦听器？
类似的东西：
public static void main(String[] args) {
setInstanceListener(listener); // this method doesn't exists
MyObject obj = new MyObject(); // the new keyword now call listener()
OtherObject oo = new OtherObject(); // same here
}
public static void listener(Object newObject) {
// do something with the created object
}
答案 0 :(得分：1)
如果您已准备好使用某些框架作为AspectJ，那么它非常简单。 在此，我将举一个使用Maven的例子。
首先是pom：
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>dummy.listener</groupId>
<artifactId>dummy.listener</artifactId>
<version>0.0.1-SNAPSHOT</version>
<description>
Is it possible in java to listen all objects creation?
http://stackoverflow.com/questions/34839701/is-it-possible-in-java-to-listen-all-objects-creation
</description>
<properties>
<main.class>dummy.listener.MainApp</main.class>
<jdk.version>1.7</jdk.version>
<project.encoding>UTF-8</project.encoding>
<project.build.sourceEncoding>${project.encoding}</project.build.sourceEncoding>
<project.reporting.outputEncoding>${project.encoding}</project.reporting.outputEncoding>
<maven.compiler.source>${jdk.version}</maven.compiler.source>
<maven.compiler.target>${jdk.version}</maven.compiler.target>
<maven.compiler.compilerVersion>${jdk.version}</maven.compiler.compilerVersion>
<maven.compiler.fork>true</maven.compiler.fork>
<maven.compiler.verbose>true</maven.compiler.verbose>
<maven.compiler.optimize>true</maven.compiler.optimize>
<maven.compiler.debug>true</maven.compiler.debug>
<maven.jar.plugin.version>2.6</maven.jar.plugin.version>
<maven.antrun.plugin.version>1.8</maven.antrun.plugin.version>
<aspectj.maven.plugin.version>1.8</aspectj.maven.plugin.version>
<aspectj.version>1.8.7</aspectj.version>
<slf4j.version>1.7.13</slf4j.version>
</properties>
<dependencies>
<!-- compile time weaving -->
<!-- required to avoid warning from aspectj-maven-plugin,
even if aspectjweaver is also a dependency -->
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>${aspectj.version}</version>
</dependency>
<!-- aspectjrt is only a subset of aspectjweaver -->
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>${aspectj.version}</version>
</dependency>
<!-- logging -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>${slf4j.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</artifactId>
</plugin>
</plugins>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</artifactId>
<version>${aspectj.maven.plugin.version}</version>
<configuration>
<complianceLevel>${jdk.version}</complianceLevel>
<showWeaveInfo>true</showWeaveInfo>
</configuration>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>test-compile</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</pluginManagement>
</build>
<profiles>
<profile>
<id>class-antrun</id>
<build>
<plugins>
<plugin>
<artifactId>maven-antrun-plugin</artifactId>
<version>${maven.antrun.plugin.version}</version>
<configuration>
<target>
<java fork="true" classname="${main.class}">
<classpath refid="maven.compile.classpath" />
</java>
</target>
</configuration>
</plugin>
</plugins>
</build>
</profile>
<profile>
<id>only-under-eclipse</id>
<activation>
<property>
<name>m2e.version</name>
</property>
</activation>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.eclipse.m2e</groupId>
<artifactId>lifecycle-mapping</artifactId>
<version>1.0.0</version>
<configuration>
<lifecycleMappingMetadata>
<pluginExecutions>
<pluginExecution>
<pluginExecutionFilter>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</artifactId>
<versionRange>[${aspectj.maven.plugin.version},)</versionRange>
<goals>
<goal>compile</goal>
<goal>test-compile</goal>
</goals>
</pluginExecutionFilter>
<action>
<ignore />
</action>
</pluginExecution>
</pluginExecutions>
</lifecycleMappingMetadata>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
</profile>
</profiles>
</project>
然后是主要课程：
package dummy.listener;
import dummy.listener.model.MyObject1;
import dummy.listener.model.MyObject2;
public class MainApp {
public static void main(final String[] args) {
new MyObject1();
new MyObject2();
}
}
编织工作由以下人员完成：
package dummy.listener;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.Aspect;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import dummy.listener.model.MyObject1;
import dummy.listener.model.MyObject2;
@Aspect
public class AspectjDemo
{
private final Logger log = LoggerFactory.getLogger(AspectjDemo.class);
@AfterReturning(pointcut="call(dummy.listener.model.*.new(..))", returning="result")
public void doSomethingAfterNewModelCreation(JoinPoint joinPoint , Object result) {
log.info("[AspectJ] Log after creation of " + result.getClass());
if (/*result instanceof MyObject1*/ MyObject1.class.isAssignableFrom(result.getClass())) {
MyObject1 mo = (MyObject1) result;
log.info("Name: " + mo.getName());
} else if (/*result instanceof MyObject2*/ MyObject2.class.isAssignableFrom(result.getClass())) {
MyObject2 mo = (MyObject2) result;
log.info("Location: " + mo.getLocation());
}
}
}
现在添加一些豚鼠类：
package dummy.listener.model;
public class MyObject1 {
public String getName() {
return "myObject1 name";
}
}
package dummy.listener.model;
public class MyObject2 {
public String getLocation() {
return "myObject2 location";
}
}
使用Maven完成，编译和启动主类：
mvn clean compile antrun:run -Pclass-antrun
你应该有类似的东西：
[...]
[INFO] --- aspectj-maven-plugin:1.8:compile (default) @ dummy.listener ---
[INFO] Showing AJC message detail for messages of types: [error, warning, fail]
[INFO] Join point 'constructor-call(void dummy.listener.model.MyObject1.<init>())' in Type 'dummy.listener.MainApp' (MainApp.java:8) advised by afterReturning advice from 'dummy.listener.AspectjDemo' (AspectjDemo.java:18)
[INFO] Join point 'constructor-call(void dummy.listener.model.MyObject2.<init>())' in Type 'dummy.listener.MainApp' (MainApp.java:9) advised by afterReturning advice from 'dummy.listener.AspectjDemo' (AspectjDemo.java:18)
[INFO]
[INFO] --- maven-antrun-plugin:1.8:run (default-cli) @ dummy.listener ---
[INFO] Executing tasks
main:
[java] [main] INFO dummy.listener.AspectjDemo - [AspectJ] Log after creation of class dummy.listener.model.MyObject1
[java] [main] INFO dummy.listener.AspectjDemo - Name: myObject1 name
[java] [main] INFO dummy.listener.AspectjDemo - [AspectJ] Log after creation of class dummy.listener.model.MyObject2
[java] [main] INFO dummy.listener.AspectjDemo - Location: myObject2 location
[INFO] Executed tasks
[...]
那就是它。希望它能帮到你。