Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.servicecomb.common.javassist; import static java.util.Locale.ENGLISH; import java.lang.reflect.Modifier; import java.nio.charset.StandardCharsets; import java.util.Arrays; import java.util.List; import org.apache.servicecomb.foundation.common.utils.JvmUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.google.common.hash.Hashing; import javassist.CannotCompileException; import javassist.ClassPool; import javassist.CtClass; import javassist.CtConstructor; import javassist.CtField; import javassist.CtMethod; import javassist.scopedpool.ScopedClassPoolRepositoryImpl; public final class JavassistUtils { private static final Logger LOGGER = LoggerFactory.getLogger(JavassistUtils.class); static { ScopedClassPoolRepositoryImpl.getInstance().setClassPoolFactory(new StdScopedClassPoolFactory()); } public static ClassPool getOrCreateClassPool(ClassLoader classLoader) { return ScopedClassPoolRepositoryImpl.getInstance().registerClassLoader(classLoader); } public static void clearByClassLoader(ClassLoader classLoader) { ScopedClassPoolRepositoryImpl.getInstance().unregisterClassLoader(classLoader); } private JavassistUtils() { } @SuppressWarnings("rawtypes") public static Class<? extends Enum> createEnum(String clsName, String... values) { return createEnum(null, clsName, Arrays.asList(values)); } @SuppressWarnings("rawtypes") public static Class<? extends Enum> createEnum(String clsName, List<String> values) { return createEnum(null, clsName, values); } @SuppressWarnings("rawtypes") public static Class<? extends Enum> getOrCreateEnumWithPackageName(ClassLoader classLoader, String packageName, List<String> enums) { String strEnums = enums.toString(); String enumClsName = packageName + ".Enum_" + Hashing.sha256().hashString(strEnums, StandardCharsets.UTF_8).toString(); return JavassistUtils.getOrCreateEnumWithClassName(classLoader, enumClsName, enums); } @SuppressWarnings({ "rawtypes", "unchecked" }) public static synchronized Class<? extends Enum> getOrCreateEnumWithClassName(ClassLoader classLoader, String clsName, List<String> values) { try { return (Class<? extends Enum>) classLoader.loadClass(clsName); } catch (ClassNotFoundException e) { return createEnum(classLoader, clsName, values); } } @SuppressWarnings({ "rawtypes", "unchecked" }) public static Class<? extends Enum> createEnum(ClassLoader classLoader, String clsName, List<String> values) { if (values == null || values.size() == 0) { throw new Error("values is not allowed empty."); } classLoader = JvmUtils.correctClassLoader(classLoader); ClassPool classPool = getOrCreateClassPool(classLoader); CtClass ctClass = classPool.makeClass(clsName); ctClass.setModifiers(ctClass.getModifiers() | javassist.Modifier.ENUM); try { ctClass.setSuperclass(classPool.get(Enum.class.getName())); addEnumConstructor(classPool, ctClass); addEnumValuesMethod(ctClass, values); return ctClass.toClass(classLoader, null); } catch (Throwable e) { throw new Error(e); } } private static void addEnumConstructor(ClassPool classPool, CtClass ctClass) throws Exception { String src = "super($1, $2);"; CtConstructor ctConstructor = new CtConstructor( classPool.get(new String[] { String.class.getName(), int.class.getName() }), ctClass); ctConstructor.setBody(src); ctClass.addConstructor(ctConstructor); } private static void addEnumValuesMethod(CtClass ctClass, List<String> values) throws CannotCompileException { StringBuilder sb = new StringBuilder(); sb.append("public static Enum[] values(){return new Enum[]{"); for (int idx = 0; idx < values.size(); idx++) { String value = values.get(idx); String line = String.format("new %s(\"%s\", %d),", ctClass.getName(), value, idx); sb.append(line); } sb.setLength(sb.length() - 1); sb.append("};}"); CtMethod valuesMethod = CtMethod.make(sb.toString(), ctClass); ctClass.addMethod(valuesMethod); } public static Class<?> createClass(ClassConfig config) { return createClass(null, config); } public static CtClass createCtClass(ClassLoader classLoader, ClassConfig config) { classLoader = JvmUtils.correctClassLoader(classLoader); ClassPool classPool = getOrCreateClassPool(classLoader); CtClass ctClass = classPool.getOrNull(config.getClassName()); if (ctClass == null) { if (config.isIntf()) { ctClass = classPool.makeInterface(config.getClassName()); } else { ctClass = classPool.makeClass(config.getClassName()); } } try { for (String intfName : config.getIntfList()) { ctClass.addInterface(classPool.get(intfName)); } for (FieldConfig fieldConfig : config.getFieldList()) { CtField field = createCtField(ctClass, fieldConfig); ctClass.addField(field); if (fieldConfig.isGenGetter()) { addFieldGetter(config, fieldConfig); } if (fieldConfig.isGenSetter()) { addFieldSetter(config, fieldConfig); } } for (MethodConfig methodConfig : config.getMethodList()) { try { CtMethod ctMethod = CtMethod.make(methodConfig.getSource(), ctClass); if (methodConfig.getGenericSignature() != null) { ctMethod.setGenericSignature(methodConfig.getGenericSignature()); } ctClass.addMethod(ctMethod); } catch (CannotCompileException e) { LOGGER.error("Failed to create method, source:\n{}.", methodConfig.getSource()); throw e; } } LOGGER.info("create CtClass {} in classLoader {}.", config.getClassName(), classLoader); return ctClass; } catch (Throwable e) { throw new IllegalStateException(String.format("Failed to create CtClass %s in classLoader %s.", config.getClassName(), classLoader), e); } } public static Class<?> createClass(ClassLoader classLoader, ClassConfig config) { classLoader = JvmUtils.correctClassLoader(classLoader); CtClass ctClass = createCtClass(classLoader, config); return createClass(classLoader, ctClass); } public static Class<?> createClass(ClassLoader classLoader, CtClass ctClass) { classLoader = JvmUtils.correctClassLoader(classLoader); String clsName = ctClass.getName(); try { // must try load from classloader first // because class A depend on class B // when load class A, will load class B // after this, if CtClass B invoke toClass again, will cause problem. return classLoader.loadClass(clsName); } catch (ClassNotFoundException e) { // ignore it } try { Class<?> cls = ctClass.toClass(classLoader, null); LOGGER.info("create class {} in classLoader {}.", clsName, classLoader); return cls; } catch (Throwable e) { throw new IllegalStateException( String.format("Failed to create %s in classLoader %s.", clsName, classLoader), e); } } public static String capitalize(String name) { if (name == null || name.length() == 0) { return name; } return name.substring(0, 1).toUpperCase(ENGLISH) + name.substring(1); } private static void addFieldGetter(ClassConfig config, FieldConfig fieldConfig) { MethodConfig methodConfig = new MethodConfig(); String prefix = "get"; if (boolean.class.getName().equals(fieldConfig.getType().getCtClass().getName()) || Boolean.class.getName().equals(fieldConfig.getType().getCtClass().getName())) { prefix = "is"; } methodConfig.setName(prefix + capitalize(fieldConfig.getName())); methodConfig.setResult(fieldConfig.getType()); methodConfig.setBodySource("return " + fieldConfig.getName() + ";"); config.addMethod(methodConfig); } private static void addFieldSetter(ClassConfig config, FieldConfig fieldConfig) { MethodConfig methodConfig = new MethodConfig(); methodConfig.setName("set" + capitalize(fieldConfig.getName())); methodConfig.addParameter(fieldConfig.getName(), fieldConfig.getType()); methodConfig.setBodySource(" this." + fieldConfig.getName() + " = " + fieldConfig.getName() + ";"); config.addMethod(methodConfig); } public static void genMultiWrapperInterface(ClassConfig config) { try { config.addInterface(MultiWrapper.class); config.addMethod(genReadFieldsMethodSource(config.getFieldList())); config.addMethod(genWriteFieldsMethodSource(config.getFieldList())); } catch (Exception e) { String msg = String.format("failed to genMultiWrapperInterface, name=%s", config.getClassName()); LOGGER.error(msg, e); throw new Error(msg, e); } } public static void genSingleWrapperInterface(ClassConfig config) { try { config.addInterface(SingleWrapper.class); config.addMethod(genReadFieldMethodSource(config.getFieldList())); config.addMethod(genWriteFieldMethodSource(config.getFieldList())); } catch (Exception e) { String msg = String.format("failed to genSingleWrapperMethod, name=%s", config.getClassName()); LOGGER.error(msg, e); throw new Error(msg, e); } } private static String genReadFieldsMethodSource(List<FieldConfig> fieldList) { StringBuilder sb = new StringBuilder(); sb.append("public Object[] readFields(){"); sb.append(String.format("Object values[] = new Object[%d];", fieldList.size())); for (int idx = 0; idx < fieldList.size(); idx++) { String fieldName = fieldList.get(idx).getName(); String code = String.format(" values[%d] = %s;", idx, fieldName); sb.append(code); } sb.append("return values;"); sb.append("}"); return sb.toString(); } private static String genWriteFieldsMethodSource(List<FieldConfig> fieldList) { StringBuilder sb = new StringBuilder(); sb.append("public void writeFields(Object[] values){"); for (int idx = 0; idx < fieldList.size(); idx++) { FieldConfig fieldConfig = fieldList.get(idx); String fieldName = fieldConfig.getName(); String code = String.format(" %s = (%s)values[%d];", fieldName, fieldConfig.getType().getCtClass().getName(), idx); sb.append(code); } sb.append("}"); return sb.toString(); } private static String genReadFieldMethodSource(List<FieldConfig> fieldList) { StringBuilder sb = new StringBuilder(); sb.append("public Object readField(){"); String fieldName = "null"; if (!fieldList.isEmpty()) { fieldName = fieldList.get(0).getName(); } sb.append(String.format(" return %s;", fieldName)); sb.append("}"); return sb.toString(); } private static String genWriteFieldMethodSource(List<FieldConfig> fieldList) { StringBuilder sb = new StringBuilder(); sb.append("public void writeField(Object value){"); if (!fieldList.isEmpty()) { FieldConfig fieldConfig = fieldList.get(0); sb.append(String.format(" %s=(%s)value;", fieldConfig.getName(), fieldConfig.getType().getCtClass().getName())); } sb.append("}"); return sb.toString(); } private static CtField createCtField(CtClass ctClass, FieldConfig field) throws CannotCompileException { CtField ctField = new CtField(field.getType().getCtClass(), field.getName(), ctClass); if (field.getType().hasGenericTypes()) { ctField.setGenericSignature(field.getType().getGenericSignature()); } ctField.setModifiers(Modifier.PUBLIC); return ctField; } }