javaagent學習

時間 2019-11-15

原文原文鏈接

序

AOP和IOC是J2EE的兩大基石，傳統的AOP是在代碼層面的，在bytecode層面也有aop技術，就是基於JVMTI(JVM TOOL INTERFACE)的instrument技術。這裏主要記錄下instrument入門使用。html

agent實例

public class SimpleJavaAgent {

    public static void premain(String args, Instrumentation instrumentation){
        System.out.println("Premain");
        System.out.println("Number of classes loaded: "+instrumentation.getAllLoadedClasses().length);
//        instrumentation.addTransformer(new DemoTransformer());
    }
}

maven打包

<build>
        <plugins>
            <!--<plugin>-->
                <!--<groupId>org.apache.maven.plugins</groupId>-->
                <!--<artifactId>maven-jar-plugin</artifactId>-->
                <!--<version>2.6</version>-->
                <!--<configuration>-->
                    <!--<outputDirectory>${basedir}</outputDirectory>-->
                    <!--<archive>-->
                        <!--&lt;!&ndash;<index>true</index>&ndash;&gt;-->
                        <!--<manifest>-->
                            <!--<addClasspath>true</addClasspath>-->
                        <!--</manifest>-->
                        <!--<manifestEntries>-->
                            <!--<Premain-Class>com.geekyarticles.instrumentation.SimpleJavaAgent</Premain-Class>-->
                        <!--</manifestEntries>-->
                    <!--</archive>-->
                <!--</configuration>-->
            <!--</plugin>-->

            <!--mvn assembly:single -->
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <outputDirectory>${basedir}</outputDirectory>
                    <archive>
                        <index>true</index>
                        <manifest>
                            <addClasspath>true</addClasspath>
                        </manifest>
                        <manifestEntries>
                            <Premain-Class>com.geekyarticles.instrumentation.SimpleJavaAgent</Premain-Class>
                        </manifestEntries>
                    </archive>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
            </plugin>
        </plugins>
    </build>

執行mvn assembly:singlejava

main實例

public class SimpleJavaAgentDemo {
    public static void main(String[] args) {
        System.out.println("Hello! its the main method");
    }
}

exec的maven配置

<build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>exec</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <executable>java</executable>
                    <arguments>
                        <!--<argument>-Xmx128m</argument>-->
                        <argument>-javaagent:"${project.parent.basedir}${file.separator}simple-agent${file.separator}simple-agent-1.0-SNAPSHOT-jar-with-dependencies.jar"</argument>
                        <argument>-classpath</argument>
                        <classpath/>
                        <argument>com.geekyarticles.instrumentation.SimpleJavaAgentDemo</argument>
                    </arguments>
                </configuration>
            </plugin>
        </plugins>
    </build>

執行mvn compile，而後mvn exec:execgit