Merge pull request eugenp#9428 from SmartyAnsh/BAEL-View_Bytecode_of_a_Class_File_in_Java

eric-martin · web-flow · commit 32bccf1c2bb9 · 2020-06-11T21:15:24.000-05:00
BAEL-4049 View bytecode of a class file in java
diff --git a/core-java-modules/core-java-jvm/pom.xml b/core-java-modules/core-java-jvm/pom.xml
@@ -51,14 +51,31 @@
             <scope>system</scope>
             <systemPath>${java.home}/../lib/tools.jar</systemPath>
         </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm</artifactId>
+            <version>${asm.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-util</artifactId>
+            <version>${asm.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.bcel</groupId>
+            <artifactId>bcel</artifactId>
+            <version>${bcel.version}</version>
+        </dependency>    
     </dependencies>
 
     <properties>
         <assertj.version>3.6.1</assertj.version>
         <!-- instrumentation -->
-        <javaassist.version>3.21.0-GA</javaassist.version>
+        <javaassist.version>3.27.0-GA</javaassist.version>
         <esapi.version>2.1.0.1</esapi.version>
         <sun.tools.version>1.8.0</sun.tools.version>
+        <asm.version>8.0.1</asm.version>
+        <bcel.version>6.5.0</bcel.version>
     </properties>
 
 </project>
diff --git a/core-java-modules/core-java-jvm/src/test/java/com/baeldung/bytecode/ViewBytecodeUnitTest.java b/core-java-modules/core-java-jvm/src/test/java/com/baeldung/bytecode/ViewBytecodeUnitTest.java
@@ -0,0 +1,51 @@
+package com.baeldung.bytecode;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+
+import org.apache.bcel.Repository;
+import org.apache.bcel.classfile.JavaClass;
+import org.junit.Test;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.util.TraceClassVisitor;
+import javassist.ClassPool;
+import javassist.NotFoundException;
+import javassist.bytecode.ClassFile;
+
+public class ViewBytecodeUnitTest {
+    
+    @Test
+    public void whenUsingASM_thenReadBytecode() throws IOException {
+        ClassReader reader = new ClassReader("java.lang.Object");
+        StringWriter sw = new StringWriter();
+        TraceClassVisitor tcv = new TraceClassVisitor(new PrintWriter(sw));
+        reader.accept(tcv, 0); 
+        
+        assertTrue(sw.toString().contains("public class java/lang/Object")); 
+    }
+    
+    @Test
+    public void whenUsingBCEL_thenReadBytecode() throws ClassNotFoundException {
+        JavaClass objectClazz = Repository.lookupClass("java.lang.Object");
+        
+        assertEquals(objectClazz.getClassName(), "java.lang.Object");   
+        assertEquals(objectClazz.getMethods().length, 14);
+        assertTrue(objectClazz.toString().contains("public class java.lang.Object"));
+    }
+    
+    @Test
+    public void whenUsingJavassist_thenReadBytecode() throws NotFoundException {
+        ClassPool cp = ClassPool.getDefault();
+        ClassFile cf = cp.get("java.lang.Object").getClassFile();
+        
+        assertEquals(cf.getName(), "java.lang.Object");
+        assertEquals(cf.getMethods().size(), 14);
+    }
+    
+}
+
+
