我一直在写一个修改加载类的字节码的Java代理。 我的代码由4类:为什么我的Javassist类没有在运行时执行?
- StackTraceAgent.java - 类的java剂与方法 的premain。
- StackTraceClassTransformer.java - 实现 java.lang.instrument.ClassFileTransformer。
- Student.java - 只是用于测试的自定义类。
- AgentTest - 具有方法main的简单类。
可利用的库:
- 了Javassist-3.20.0-GA.jar
StackTraceAgent.java,ClassFileTransformer.java和了Javassist-3.20.0-GA.jar被包装在一个jar文件。它通过“-javaagent:MyJar.jar AgentTest”调用。我的问题是,使用javassist类编写的代码已经在runtume中调用。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。
我如何试图解决这一问题:
- 我已审阅编译的类。所有类都包含确切的代码。
- 我觉得它是包装成jar的东西有问题,但经过几个小时的上网冲浪,我没有找到任何有趣的东西。
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
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;
}
}
在wour清单文件,你不表示任何类路径,特别是对于依赖,是故意的吗? – Adonis
你可以给我一些建议吗?我想了解更多有关manifest的类。 –
谢谢你的建议。 –