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 javax.el; import java.beans.FeatureDescriptor; import java.util.Iterator; import java.util.NoSuchElementException; import java.util.Objects; public class CompositeELResolver extends ELResolver { private static final Class<?> SCOPED_ATTRIBUTE_EL_RESOLVER; static { Class<?> clazz = null; try { clazz = Class.forName("javax.servlet.jsp.el.ScopedAttributeELResolver"); } catch (ClassNotFoundException e) { // Ignore. This is expected if using the EL stand-alone } SCOPED_ATTRIBUTE_EL_RESOLVER = clazz; } private int size; private ELResolver[] resolvers; public CompositeELResolver() { this.size = 0; this.resolvers = new ELResolver[8]; } public void add(ELResolver elResolver) { Objects.requireNonNull(elResolver); if (this.size >= this.resolvers.length) { ELResolver[] nr = new ELResolver[this.size * 2]; System.arraycopy(this.resolvers, 0, nr, 0, this.size); this.resolvers = nr; } this.resolvers[this.size++] = elResolver; } @Override public Object getValue(ELContext context, Object base, Object property) { context.setPropertyResolved(false); int sz = this.size; for (int i = 0; i < sz; i++) { Object result = this.resolvers[i].getValue(context, base, property); if (context.isPropertyResolved()) { return result; } } return null; } /** * @since EL 2.2 */ @Override public Object invoke(ELContext context, Object base, Object method, Class<?>[] paramTypes, Object[] params) { context.setPropertyResolved(false); int sz = this.size; for (int i = 0; i < sz; i++) { Object obj = this.resolvers[i].invoke(context, base, method, paramTypes, params); if (context.isPropertyResolved()) { return obj; } } return null; } @Override public Class<?> getType(ELContext context, Object base, Object property) { context.setPropertyResolved(false); int sz = this.size; for (int i = 0; i < sz; i++) { Class<?> type = this.resolvers[i].getType(context, base, property); if (context.isPropertyResolved()) { if (SCOPED_ATTRIBUTE_EL_RESOLVER != null && SCOPED_ATTRIBUTE_EL_RESOLVER.isAssignableFrom(resolvers[i].getClass())) { // Special case since // javax.servlet.jsp.el.ScopedAttributeELResolver will // always return Object.class for type Object value = resolvers[i].getValue(context, base, property); if (value != null) { return value.getClass(); } } return type; } } return null; } @Override public void setValue(ELContext context, Object base, Object property, Object value) { context.setPropertyResolved(false); int sz = this.size; for (int i = 0; i < sz; i++) { this.resolvers[i].setValue(context, base, property, value); if (context.isPropertyResolved()) { return; } } } @Override public boolean isReadOnly(ELContext context, Object base, Object property) { context.setPropertyResolved(false); int sz = this.size; for (int i = 0; i < sz; i++) { boolean readOnly = this.resolvers[i].isReadOnly(context, base, property); if (context.isPropertyResolved()) { return readOnly; } } return false; } @Override public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) { return new FeatureIterator(context, base, this.resolvers, this.size); } @Override public Class<?> getCommonPropertyType(ELContext context, Object base) { Class<?> commonType = null; int sz = this.size; for (int i = 0; i < sz; i++) { Class<?> type = this.resolvers[i].getCommonPropertyType(context, base); if (type != null && (commonType == null || commonType.isAssignableFrom(type))) { commonType = type; } } return commonType; } @Override public Object convertToType(ELContext context, Object obj, Class<?> type) { context.setPropertyResolved(false); int sz = this.size; for (int i = 0; i < sz; i++) { Object result = this.resolvers[i].convertToType(context, obj, type); if (context.isPropertyResolved()) { return result; } } return null; } private static final class FeatureIterator implements Iterator<FeatureDescriptor> { private final ELContext context; private final Object base; private final ELResolver[] resolvers; private final int size; private Iterator<FeatureDescriptor> itr; private int idx; private FeatureDescriptor next; public FeatureIterator(ELContext context, Object base, ELResolver[] resolvers, int size) { this.context = context; this.base = base; this.resolvers = resolvers; this.size = size; this.idx = 0; this.guaranteeIterator(); } private void guaranteeIterator() { while (this.itr == null && this.idx < this.size) { this.itr = this.resolvers[this.idx].getFeatureDescriptors(this.context, this.base); this.idx++; } } @Override public boolean hasNext() { if (this.next != null) return true; if (this.itr != null) { while (this.next == null && itr.hasNext()) { this.next = itr.next(); } } else { return false; } if (this.next == null) { this.itr = null; this.guaranteeIterator(); } return hasNext(); } @Override public FeatureDescriptor next() { if (!hasNext()) { throw new NoSuchElementException(); } FeatureDescriptor result = this.next; this.next = null; return result; } @Override public void remove() { throw new UnsupportedOperationException(); } } }