package com.shihuan.asm.account;
public class Account {
public void operation() {
System.out.println("shihuan operation...");
}
}
package com.shihuan.asm.account;
public class SecurityChecker {
public static void checkSecurity() {
System.out.println("SecurityChecker.checkSecurity...");
}
}
package com.shihuan.asm.account;
public class TestAccount {
public static void main(String[] args) {
Account a = new Account();
a.operation();
}
}
package com.shihuan.asm.account;
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 AccountAsm {
public static void main(String[] args) throws IOException {
ClassReader cr = new ClassReader("com.shihuan.asm.account.Account");
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) {
MethodVisitor mv = cv.visitMethod(access, name, desc, signature, exceptions); // 先得到原始的方法
MethodVisitor newMethod = mv;
if (mv != null) {
if ("operation".equals(name)){ // 此处的operation即为需要修改的方法 ，修改方法內容
// 访问需要修改的方法
newMethod = new MethodVisitor(Opcodes.ASM5, mv) {
public void visitCode() {
visitMethodInsn(Opcodes.INVOKESTATIC, "com/shihuan/asm/account/SecurityChecker","checkSecurity", "()V", false);
super.visitCode();
}
};
}
}
return newMethod;
}
};
cr.accept(cv, ClassReader.SKIP_DEBUG);
byte[] code = cw.toByteArray();
OutputStream fos = new FileOutputStream("D:/myworkspace/JavaAsm/bin/com/shihuan/asm/account/Account.class");
fos.write(code);
fos.close();
}
}
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上面的代码是笔者测试Asm用的，下面笔者做一个抓取Oracle驱动包中原生态SQL语句的例子。
需要在工程中添加ojdbc6.jar文件。
package oracle.jdbc.driver;
public class OracleMyEnd {
public static void getMySqlInfo(OraclePreparedStatement opsObj) {
System.out.println("ShiHuan Is Sql --->> " + opsObj.sqlObject.originalSql);
}
}
package oracle.jdbc.driver;
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 OracleAsm {
public static void main(String[] args) {
try {
ClassReader cr = new ClassReader("oracle.jdbc.driver.OraclePreparedStatement");
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) {
MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions); // 先得到原始的方法
MethodVisitor newMethod = mv;
if (mv != null) {
if ("executeInternal".equals(name)){ // 此处的executeInternal即为需要修改的方法 ，修改方法內容
// 访问需要修改的方法
newMethod = new MethodVisitor(Opcodes.ASM5, newMethod) {
public void visitCode() {
visitVarInsn(Opcodes.ALOAD, 0);
visitMethodInsn(Opcodes.INVOKESTATIC, "oracle/jdbc/driver/OracleMyEnd","getMySqlInfo", "(Loracle/jdbc/driver/OraclePreparedStatement;)V", false);
super.visitCode();
}
};
}
}
return newMethod;
}
};
cr.accept(cv, ClassReader.SKIP_DEBUG);
byte[] code = cw.toByteArray();
OutputStream fos = new FileOutputStream("D:/myworkspace/JavaAsm/bin/oracle/jdbc/driver/OraclePreparedStatement.class");
fos.write(code);
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}