The document discusses various classes and methods for code generation and runtime interfaces in Java, emphasizing secure access control via annotations. It includes details on using Mockito for mocking behaviors in class methods and describes the configuration and usage of the Kotlin Maven plugin. Additionally, it highlights build-time instrumentation using the Byte Buddy library along with examples of class transformations.

1. Code generation for
alternative languages
and Java runtimes

2. interface Framework {
<T> Class<? extends T> secure(Class<T> type);
}
class Service {
@Secured(user = "ADMIN")
void deleteEverything() {
// delete everything...
}
}
@interface Secured {
String user();
}
class UserHolder {
static String user = "ANONYMOUS";
}
does not know aboutdepends on
discoversatruntime

3. class Service {
@Secured(user = "ADMIN")
void deleteEverything() {
if(!"ADMIN".equals(UserHolder.user)) {
throw new IllegalStateException("Wrong user");
}
// delete everything...
}
}
redefine class
(build time, agent)
create subclass
(Liskov substitution)
class SecuredService extends Service {
@Override
void deleteEverything() {
if(!"ADMIN".equals(UserHolder.user)) {
throw new IllegalStateException("Wrong user");
}
super.deleteEverything();
}
}
class Service {
@Secured(user = "ADMIN")
void deleteEverything() {
// delete everything...
}
}

4. 0xCAFEBABE
source code
byte code
JVM
javac scalac groovyc jrubyc
JIT compilerinterpreter
class loader
creates
reads
runs

6. class Sample$MockitoMock extends Sample {
@Override String getValue() {
return Mockito.mock(this,
new Object[0],
Sample.class.getMethod("getValue"));
}
String original$getValue() {
return super.getValue();
}
@Override void setValue(String x) {
Mockito.mock(this,
new Object[] { x },
Sample.class.getMethod("setValue",
String.class));
}
void original$setValue(String x) {
super.setValue(x);
}
}
class Sample {
String value;
String getValue() {
return value;
}
void setValue(String x) {
this.value = x;
}
}

7. class Sample {
var value: String? = null
fun getValue() = value
fun setValue(x: String?) {
this.value = x
}
}
final class Sample {
String value;
final String getValue() {
return value;
}
final void setValue(String x) {
this.value = x;
}
}

8. open class Sample {
var value: String? = null
open fun getValue() = value
open fun setValue(x: String?) {
this.value = x
}
}
class Sample {
String value;
String getValue() {
return value;
}
void setValue(String x) {
this.value = x;
}
}

9. <plugin>
<artifactId>kotlin-maven-plugin</artifactId>
<groupId>org.jetbrains.kotlin</groupId>
<version>${kotlin.version}</version>
<configuration>
<compilerPlugins>
<plugin>all-open</plugin>
</compilerPlugins>
<pluginOptions>
<option>all-open:annotation=pkg.MyOpen</option>
</pluginOptions>
</configuration>
<dependencies>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-maven-allopen</artifactId>
<version>${kotlin.version}</version>
</dependency>
</dependencies>
</plugin>
annotation class MyOpen

10. final class Sample {
String value;
final String getValue() {
if (MockitoInfra.isMockMode(this)) {
return Mockito.mock( this,
new Object[0],
Sample.class.getMethod("getValue"));
} else {
return value;
}
}
final void setValue(String x) {
if (MockitoInfra.isMockMode(this)) {
Mockito.mock( this,
new Object[] { x },
Sample.class.getMethod("setValue",
String.class));
} else {
this.value = x;
}
}
}
final class Sample {
String value;
final String getValue() {
return value;
}
final void setValue(String x) {
this.value = x;
}
}

11. class MockitoInfra {
static final WeakConcurrentMap<Object, MockitoHandler> mocks;
static final ThreadLocal<Boolean> selfCall;
static boolean isMock(Object instance) {
return mocks.containsKey(instance);
}
static void registerMock(Object instance, MockHandler handler) {
mocks.put(instance, handler);
}
static boolean isMockMode(Object instance) {
return isMock(instance) && selfCall.get();
}
static void setMockMode(boolean mode) {
selfCall.set(mode);
}
}
https://github.com/raphw/weak-lock-free

12. package java.lang.instrumentation;
interface Instrumentation {
void addTransformer(ClassFileTransformer transformer, boolean retransform);
void retransformClasses(Class<?>... types);
void appendToBootstrapSearch(File file);
// ...
}
interface ClassFileTransformer {
byte[] transform(ClassLoader loader,
String name,
Class<?> type,
ProtectionDomain pd,
byte[] buffer);
}
NOPE!

13. Java virtual
machine
[stack, JIT]
Dalvik virtual
machine
[register, JIT]
Android
runtime
[register, AOT]

14. public class SimplePlugin implements Plugin {
@Override
public boolean matches(TypeDescription target) {
return target.getName().equals("Foo");
}
@Override
public DynamicType.Builder<?> apply(
DynamicType.Builder<?> builder,
TypeDescription typeDescription) {
return builder.method(named("bar"))
.intercept(value("Hello World!"));
}
}
https://github.com/raphw/byte-buddy

15. Build-time instrumentation with Maven.
<plugin>
<groupId>net.bytebuddy</groupId>
<artifactId>byte-buddy-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>transform</goal>
</goals>
</execution>
</executions>
<configuration>
<transformations>
<transformation>
<plugin>pkg.SimplePlugin</plugin>
</transformation>
</transformations>
</configuration>
</plugin>

16. http://rafael.codes
@rafaelcodes
http://documents4j.com
https://github.com/documents4j/documents4j
http://bytebuddy.net
https://github.com/raphw/byte-buddy