A Java-language API for doing compile time or runtime code generation targeting the Dalvik VM. Unlike
cglib or ASM, this library creates Dalvik .dex
files instead of Java .class
files.
It has a small, close-to-the-metal API. This API mirrors the
Dalvik bytecode specification giving you tight
control over the bytecode emitted. Code is generated instruction-by-instruction; you bring your own abstract
syntax tree if you need one. And since it uses Dalvik's dx
tool as a backend, you get efficient register
allocation and regular/wide instruction selection for free.
Dexmaker includes a stock code generator for class proxies. If you just want to do AOP or class mocking, you don't need to mess around with bytecodes.
Dexmaker includes class proxy support for Mockito. Add the mockito
and the dexmaker .jar
files to your Android test project's libs/
directory and you can use Mockito
in your Android unit tests.
This requires Mockito 1.9.5 or newer.
This example generates a class and a method. It then loads that class into the current process and invokes its method.
public final class HelloWorldMaker {
public static void main(String[] args) throws Exception {
DexMaker dexMaker = new DexMaker();
// Generate a HelloWorld class.
TypeId<?> helloWorld = TypeId.get("LHelloWorld;");
dexMaker.declare(helloWorld, "HelloWorld.generated", Modifier.PUBLIC, TypeId.OBJECT);
generateHelloMethod(dexMaker, helloWorld);
// Create the dex file and load it.
File outputDir = new File(".");
ClassLoader loader = dexMaker.generateAndLoad(HelloWorldMaker.class.getClassLoader(),
outputDir, outputDir);
Class<?> helloWorldClass = loader.loadClass("HelloWorld");
// Execute our newly-generated code in-process.
helloWorldClass.getMethod("hello").invoke(null);
}
/**
* Generates Dalvik bytecode equivalent to the following method.
* public static void hello() {
* int a = 0xabcd;
* int b = 0xaaaa;
* int c = a - b;
* String s = Integer.toHexString(c);
* System.out.println(s);
* return;
* }
*/
private static void generateHelloMethod(DexMaker dexMaker, TypeId<?> declaringType) {
// Lookup some types we'll need along the way.
TypeId<System> systemType = TypeId.get(System.class);
TypeId<PrintStream> printStreamType = TypeId.get(PrintStream.class);
// Identify the 'hello()' method on declaringType.
MethodId hello = declaringType.getMethod(TypeId.VOID, "hello");
// Declare that method on the dexMaker. Use the returned Code instance
// as a builder that we can append instructions to.
Code code = dexMaker.declare(hello, Modifier.STATIC | Modifier.PUBLIC);
// Declare all the locals we'll need up front. The API requires this.
Local<Integer> a = code.newLocal(TypeId.INT);
Local<Integer> b = code.newLocal(TypeId.INT);
Local<Integer> c = code.newLocal(TypeId.INT);
Local<String> s = code.newLocal(TypeId.STRING);
Local<PrintStream> localSystemOut = code.newLocal(printStreamType);
// int a = 0xabcd;
code.loadConstant(a, 0xabcd);
// int b = 0xaaaa;
code.loadConstant(b, 0xaaaa);
// int c = a - b;
code.op(BinaryOp.SUBTRACT, c, a, b);
// String s = Integer.toHexString(c);
MethodId<Integer, String> toHexString
= TypeId.get(Integer.class).getMethod(TypeId.STRING, "toHexString", TypeId.INT);
code.invokeStatic(toHexString, s, c);
// System.out.println(s);
FieldId<System, PrintStream> systemOutField = systemType.getField(printStreamType, "out");
code.sget(systemOutField, localSystemOut);
MethodId<PrintStream, Void> printlnMethod = printStreamType.getMethod(
TypeId.VOID, "println", TypeId.STRING);
code.invokeVirtual(printlnMethod, null, localSystemOut, s);
// return;
code.returnVoid();
}
}
Maven users can get dexmaker from Sonatype's central repository. The Mockito dependency is optional.
<dependency>
<groupId>com.google.dexmaker</groupId>
<artifactId>dexmaker</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>com.google.dexmaker</groupId>
<artifactId>dexmaker-mockito</artifactId>
<version>1.2</version>
</dependency>
Download dexmaker-1.2.jar and dexmaker-mockito-1.2.jar.