Javaバイトコード削除またはクラスメソッドの追加
次のコードはasm-5.0.2.jarとasm-commons-5.0.2.jarの2つのパッケージが必要です.
AsmAddMethod 2.javaはAccountMethod.javaファイルのすべての内容をクリアし、新しいメソッドを追加しますが、一般的には使用することは少ないです.
package com.shihuan.method;
public class AccountMethod {
String sql = "select * from tables";
public AccountMethod() {
}
public AccountMethod(String sql) {
super();
this.sql = sql;
}
public void operation() {
System.out.println("shihuan operation...");
}
int executeInternal() {
System.out.println("shihuan executeInternal...");
if (true) {
System.out.println(this.sql);
return 2;
}
return 3;
}
}
package com.shihuan.method;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.commons.GeneratorAdapter;
import org.objectweb.asm.commons.Method;
public class AsmAddMethod {
public static void main(String[] args) throws IOException {
ClassReader cr = new ClassReader("com.shihuan.method.AccountMethod");
ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS);
ClassVisitor cv = new ClassVisitor(Opcodes.ASM5, cw){};
cr.accept(cv, Opcodes.ASM5);
//
MethodVisitor mw= cw.visitMethod(Opcodes.ACC_PUBLIC + Opcodes.ACC_STATIC,
"add",
"([Ljava/lang/String;)V",
null,
null);
// pushes the 'out' field (of type PrintStream) of the System class
mw.visitFieldInsn(Opcodes.GETSTATIC,
"java/lang/System",
"out",
"Ljava/io/PrintStream;");
// pushes the "Hello World!" String constant
mw.visitLdcInsn("this is add method print!");
// invokes the 'println' method (defined in the PrintStream class)
mw.visitMethodInsn(Opcodes.INVOKEVIRTUAL,
"java/io/PrintStream",
"println",
"(Ljava/lang/String;)V", false);
mw.visitInsn(Opcodes.RETURN);
// this code uses a maximum of two stack elements and two local
// variables
mw.visitMaxs(0, 0);
mw.visitEnd();
byte[] code = cw.toByteArray();
OutputStream fos = new FileOutputStream("D:/myworkspace/JavaAsm/bin/com/shihuan/method/AccountMethod.class");
fos.write(code);
fos.close();
}
}
package com.shihuan.method;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
public class AsmDeleteMethod {
public static void main(String[] args) throws IOException {
ClassReader cr = new ClassReader("com.shihuan.method.AccountMethod");
ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS);
ClassVisitor cv = new ClassVisitor(Opcodes.ASM5, cw) {
public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
if("executeInternal".equals(name)) {
return null;
}
return super.visitMethod(access, name, desc, signature, exceptions); // null,
}
};
cr.accept(cv, ClassReader.SKIP_DEBUG);
byte[] code = cw.toByteArray();
OutputStream fos = new FileOutputStream("D:/myworkspace/JavaAsm/bin/com/shihuan/method/AccountMethod.class");
fos.write(code);
fos.close();
}
}
AsmAddMethod 2.javaはAccountMethod.javaファイルのすべての内容をクリアし、新しいメソッドを追加しますが、一般的には使用することは少ないです.
package com.shihuan.method;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.commons.GeneratorAdapter;
import org.objectweb.asm.commons.Method;
public class AsmAddMethod2 {
public static void main(String[] args) throws IOException {
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
cw.visit(38, Opcodes.ACC_PUBLIC, "com.shihuan.method.AccountMethod", null, "java/lang/Object", null);
Method m = Method.getMethod("void <init> ()");
GeneratorAdapter ga = new GeneratorAdapter(Opcodes.ACC_PUBLIC, m, null, null, cw);
ga.loadThis();
ga.invokeConstructor(Type.getType(Object.class), m);
ga.returnValue();
ga.endMethod();
m = Method.getMethod("void doSomething()");
ga = new GeneratorAdapter(Opcodes.ACC_PUBLIC, m, null, null, cw);
ga.getStatic(Type.getType(System.class), "out", Type.getType(PrintStream.class));
ga.push(" , ");
ga.invokeVirtual(Type.getType(PrintStream.class), Method.getMethod("void println(String)"));
ga.returnValue();
ga.endMethod();
byte[] code = cw.toByteArray();
OutputStream fos = new FileOutputStream("D:/myworkspace/JavaAsm/bin/com/shihuan/method/AccountMethod.class");
fos.write(code);
fos.close();
}
}