ASM

asm.clj

(ns asm
  (:import liquibase.database.core.H2Database
           liquibase.database.jvm.JdbcConnection
           [org.objectweb.asm Opcodes ClassWriter Type]
           [org.objectweb.asm.commons Method GeneratorAdapter]))

(defn x ^ClassWriter []
  (let [flags 0
        classwriter (org.objectweb.asm.ClassWriter. flags)]
    ;; define the Class
    (.visit
     classwriter
     Opcodes/V1_8
     Opcodes/ACC_PUBLIC
     "metabase/db/liquibase/h2/H2Database"
     nil
     "liquibase/database/core/H2Database"
     (into-array String []))
    ;; define the constructor H2Database()
    (let [method (Method/getMethod "void <init> ()")
          generator (GeneratorAdapter. Opcodes/ACC_PUBLIC method nil nil classwriter)]
      (doto generator
        .loadThis
        (.invokeConstructor (Type/getType H2Database) method)
        .returnValue
        .endMethod))
    ;; define boolean mustQuoteObjectName(String objectName, String objectType) implementation
    (let [method (Method/getMethod "boolean mustQuoteObjectName(")])

    ;; finally, return the classwriter so we can convert it to bytes
    classwriter))

(defn y ^bytes []
  (.toByteArray (x)))

(defn z ^Class []
  (.defineClass (classloader/the-classloader)
                "metabase.db.liquibase.h2.H2Database"
                (y)
                nil))

(defn disassemble [^bytes bytecode]
  (.disassemble (org.eclipse.jdt.internal.core.util.Disassembler.) bytecode "\n" 1))

(defn a []
  (println (disassemble (y))))

(with-open [os (java.io.FileOutputStream. "/home/cam/java8.class")]
  (.write os (y)))