[JAVA-22519] Created new module libraries-stream and added 5 articles (#15403)

libraries-bytecode/src/test/java/com/baeldung/bytebuddy/ByteBuddyUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.bytebuddy;
+
+import static net.bytebuddy.matcher.ElementMatchers.isDeclaredBy;
+import static net.bytebuddy.matcher.ElementMatchers.named;
+import static net.bytebuddy.matcher.ElementMatchers.returns;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+import org.junit.Test;
+
+import net.bytebuddy.ByteBuddy;
+import net.bytebuddy.agent.ByteBuddyAgent;
+import net.bytebuddy.dynamic.DynamicType;
+import net.bytebuddy.dynamic.loading.ClassLoadingStrategy;
+import net.bytebuddy.dynamic.loading.ClassReloadingStrategy;
+import net.bytebuddy.implementation.FixedValue;
+import net.bytebuddy.implementation.MethodDelegation;
+import net.bytebuddy.matcher.ElementMatchers;
+
+public class ByteBuddyUnitTest {
+
+    @Test
+    public void givenObject_whenToString_thenReturnHelloWorldString() throws InstantiationException, IllegalAccessException {
+        DynamicType.Unloaded unloadedType = new ByteBuddy().subclass(Object.class).method(ElementMatchers.isToString()).intercept(FixedValue.value("Hello World ByteBuddy!")).make();
+
+        Class<?> dynamicType = unloadedType.load(getClass().getClassLoader()).getLoaded();
+
+        assertEquals(dynamicType.newInstance().toString(), "Hello World ByteBuddy!");
+    }
+
+    @Test
+    public void givenFoo_whenRedefined_thenReturnFooRedefined() throws Exception {
+        ByteBuddyAgent.install();
+        new ByteBuddy().redefine(Foo.class).method(named("sayHelloFoo")).intercept(FixedValue.value("Hello Foo Redefined")).make().load(Foo.class.getClassLoader(), ClassReloadingStrategy.fromInstalledAgent());
+        Foo f = new Foo();
+        assertEquals(f.sayHelloFoo(), "Hello Foo Redefined");
+    }
+
+    @Test
+    public void givenSayHelloFoo_whenMethodDelegation_thenSayHelloBar() throws IllegalAccessException, InstantiationException {
+
+        String r = new ByteBuddy().subclass(Foo.class).method(named("sayHelloFoo").and(isDeclaredBy(Foo.class).and(returns(String.class)))).intercept(MethodDelegation.to(Bar.class)).make().load(getClass().getClassLoader()).getLoaded().newInstance()
+                .sayHelloFoo();
+
+        assertEquals(r, Bar.sayHelloBar());
+    }
+
+    @Test
+    public void givenMethodName_whenDefineMethod_thenCreateMethod() throws Exception {
+        Class<?> type = new ByteBuddy().subclass(Object.class).name("MyClassName").defineMethod("custom", String.class, Modifier.PUBLIC).intercept(MethodDelegation.to(Bar.class)).defineField("x", String.class, Modifier.PUBLIC).make()
+                .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER).getLoaded();
+
+        Method m = type.getDeclaredMethod("custom", null);
+
+        assertEquals(m.invoke(type.newInstance()), Bar.sayHelloBar());
+        assertNotNull(type.getDeclaredField("x"));
+
+    }
+
+}