我一直在编写一个修改已加载类的字节码的java代理。 我的代码由4个类组成:
利用库:
StackTraceAgent.java,ClassFileTransformer.java和javassist-3.20.0-GA.jar打包在一个jar文件中。它通过" -javaagent:MyJar.jar AgentTest"调用。我的问题是,在runtume中没有调用使用javassist类编写的代码。它只是由运行时传递而没有任何错误,并且在最后程序继续执行非javassist代码直到结束。
我是如何尝试解决这个问题的:
MANIFEST.MF:
Manifest-Version: 1.0
Premain-Class: agent.StackTraceAgent
我的pom.xml文件:
<?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>com.belenov</groupId>
<artifactId>TraceAgent</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.javassist/javassist -->
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.20.0-GA</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>prepare-package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/classes/lib</outputDirectory>
<overWriteReleases>false</overWriteReleases>
<overWriteSnapshots>false</overWriteSnapshots>
<overWriteIfNewer>true</overWriteIfNewer>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifestFile>
src/main/resources/META-INF/MANIFEST.MF
</manifestFile>
<manifest>
<addClasspath>false</addClasspath>
</manifest>
</archive>
</configuration>
</plugin>
</plugins>
</build>
</project>
StackTraceAgent.java:
import java.lang.instrument.Instrumentation;
public class StackTraceAgent {
public static void premain(String args, Instrumentation instrumentation) {
System.out.println("instrument agent");
StackTraceClassTransformer transformer = new StackTraceClassTransformer();
instrumentation.addTransformer(transformer);
}
}
StackTraceClassTransformer.java:
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;
public class StackTraceClassTransformer implements ClassFileTransformer {
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
ProtectionDomain protectionDomain,
byte[] classfileBuffer) throws IllegalClassFormatException {
try {
//the code below is passed up
ClassPool classPool = ClassPool.getDefault();
CtClass ctClass = classPool.get(className);
CtMethod[] methods = ctClass.getMethods();
for (CtMethod method : methods) {
method.insertAfter("System.out.println(\"Method name: \"+" + method.getName() + "+\" \"+" + method.getSignature() + ");");
method.insertAfter("System.out.println(\"Object: \" + this.toString());");
}
byte[] byteCode = ctClass.toBytecode();
ctClass.detach();
return byteCode;
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
}
AgentTest.java
public class AgentTest {
public static void main(String[] args) {
System.out.println("Agent Tester");
Student student = new Student("vasia", "poopkin");
student.toString();
}
}
Student.java
public class Student {
private String name;
private String surname;
public Student(String name, String surname) {
this.name = name;
this.surname = surname;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", surname='" + surname + '\'' +
'}';
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSurname() {
return surname;
}
public void setSurname(String surname) {
this.surname = surname;
}
}
答案 0 :(得分:1)
基本上在您的清单文件中,您需要包含程序使用的每个库和资源的类路径,您可以在MANIFEST.MF中添加如下所示的行:
Class-Path: path/to/my/libraries
这样做的一种方法就是更新你的pom.xml,maven jar插件的manifest部分:
<addClasspath>true</addClasspath>
<classpathPrefix>${project.build.directory}/classes/lib</classpathPrefix>