Programming language: Java
License: BSD 3-clause "New" or "Revised" License
Tags: Projects     Introspection    
Latest version: v1.11.9

ReflectASM alternatives and similar libraries

Based on the "Introspection" category.
Alternatively, view ReflectASM alternatives based on common mentions on social networks and blogs.

  • Reflections

    Reflections scans your classpath, indexes the metadata, allows you to query it on runtime and may save and collect that information for many modules within your project.
  • jOOR

    jOOR stands for jOOR Object Oriented Reflection. It is a simple wrapper for the java.lang.reflect package.
  • Scout APM uses tracing logic that ties bottlenecks to source code so you know the exact line of code causing performance issues and can get back to building a great product faster.
    Sponsored scoutapm.com
  • ClassGraph

    ClassGraph (formerly FastClasspathScanner) is an uber-fast, ultra-lightweight, parallelized classpath scanner and module scanner for Java, Scala, Kotlin and other JVM languages.
  • Objenesis

    Allows dynamic instantiation without default constructor, e.g. constructors which have required arguments, side effects or throw exceptions.
  • Mirror

    Mirror was created to bring light to a simple problem, usually named ReflectionUtil, which is on almost all projects that rely on reflection to do advanced tasks.

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Build Status Maven Central

Please use the ReflectASM discussion group for support.


ReflectASM is a very small Java library that provides high performance reflection by using code generation. An access class is generated to set/get fields, call methods, or create a new instance. The access class uses bytecode rather than Java's reflection, so it is much faster. It can also access primitive fields via bytecode to avoid boxing.


The source code for these benchmarks is included in the project. The above charts were generated on Oracle's Java 7u3, server VM.


To use reflectasm with maven, please use the following snippet in your pom.xml



Method reflection with ReflectASM:

SomeClass someObject = ...
MethodAccess access = MethodAccess.get(SomeClass.class);
access.invoke(someObject, "setName", "Awesome McLovin");
String name = (String)access.invoke(someObject, "getName");

Field reflection with ReflectASM:

SomeClass someObject = ...
FieldAccess access = FieldAccess.get(SomeClass.class);
access.set(someObject, "name", "Awesome McLovin");
String name = (String)access.get(someObject, "name");

Constructor reflection with ReflectASM:

ConstructorAccess<SomeClass> access = ConstructorAccess.get(SomeClass.class);
SomeClass someObject = access.newInstance();

Avoiding Name Lookup

For maximum performance when methods or fields are accessed repeatedly, the method or field index should be used instead of the name:

SomeClass someObject = ...
MethodAccess access = MethodAccess.get(SomeClass.class);
int addNameIndex = access.getIndex("addName");
for (String name : names)
    access.invoke(someObject, addNameIndex, "Awesome McLovin");

Iterate all fields:

FieldAccess access = FieldAccess.get(SomeClass.class);
for(int i = 0, n = access.getFieldCount(); i < n; i++) {
    access.set(instanceObject, i, valueToPut);              


ReflectASM can always access public members. An attempt is made to define access classes in the same classloader (using setAccessible) and package as the accessed class. If the security manager allows setAccessible to succeed, then protected and default access (package private) members can be accessed. If setAccessible fails, no exception is thrown, but only public members can be accessed. Private members can never be accessed.


Stack traces when using ReflectASM are a bit cleaner. Here is Java's reflection calling a method that throws a RuntimeException:

Exception in thread "main" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.example.SomeCallingCode.doit(SomeCallingCode.java:22)
Caused by: java.lang.RuntimeException
    at com.example.SomeClass.someMethod(SomeClass.java:48)
    ... 5 more

Here is the same but when ReflectASM is used:

Exception in thread "main" java.lang.RuntimeException
    at com.example.SomeClass.someMethod(SomeClass.java:48)
    at com.example.SomeClassMethodAccess.invoke(Unknown Source)
    at com.example.SomeCallingCode.doit(SomeCallingCode.java:22)

If ReflectASM is used to invoke code that throws a checked exception, the checked exception is thrown. Because it is a compilation error to use try/catch with a checked exception around code that doesn't declare that exception as being thrown, you must catch Exception if you care about catching a checked exception in code you invoke with ReflectASM.