ServletResponseWrapper.java

/*
 * Copyright (c) 1997, 2022 Oracle and/or its affiliates and others.
 * All rights reserved.
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed 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 jakarta.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.nio.charset.Charset;
import java.util.Locale;

/**
 * 
 * Provides a convenient implementation of the ServletResponse interface that can be subclassed by developers wishing to
 * adapt the response from a Servlet. This class implements the Wrapper or Decorator pattern. Methods default to calling
 * through to the wrapped response object.
 * 
 * @author Various
 * @since Servlet 2.3
 *
 * @see jakarta.servlet.ServletResponse
 */
public class ServletResponseWrapper implements ServletResponse {
    private ServletResponse response;

    /**
     * Creates a ServletResponse adaptor wrapping the given response object.
     *
     * @param response the {@link ServletResponse} to be wrapped
     *
     * @throws java.lang.IllegalArgumentException if the response is null.
     */
    public ServletResponseWrapper(ServletResponse response) {
        if (response == null) {
            throw new IllegalArgumentException("Response cannot be null");
        }
        this.response = response;
    }

    /**
     * Return the wrapped ServletResponse object.
     *
     * @return the wrapped {@link ServletResponse}
     */
    public ServletResponse getResponse() {
        return this.response;
    }

    /**
     * Sets the response being wrapped.
     *
     * @param response the {@link ServletResponse} to be installed
     *
     * @throws java.lang.IllegalArgumentException if the response is null.
     */
    public void setResponse(ServletResponse response) {
        if (response == null) {
            throw new IllegalArgumentException("Response cannot be null");
        }
        this.response = response;
    }

    /**
     * The default behavior of this method is to call setCharacterEncoding(String encoding) on the wrapped response object.
     *
     * @since Servlet 2.4
     */
    @Override
    public void setCharacterEncoding(String encoding) {
        this.response.setCharacterEncoding(encoding);
    }

    /**
     * The default behavior of this method is to call setCharacterEncoding(Charset encoding) on the wrapped response object.
     *
     * @since Servlet 6.1
     */
    @Override
    public void setCharacterEncoding(Charset encoding) {
        this.response.setCharacterEncoding(encoding);
    }

    /**
     * The default behavior of this method is to return getCharacterEncoding() on the wrapped response object.
     */
    @Override
    public String getCharacterEncoding() {
        return this.response.getCharacterEncoding();
    }

    /**
     * The default behavior of this method is to return getOutputStream() on the wrapped response object.
     */
    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return this.response.getOutputStream();
    }

    /**
     * The default behavior of this method is to return getWriter() on the wrapped response object.
     */
    @Override
    public PrintWriter getWriter() throws IOException {
        return this.response.getWriter();
    }

    /**
     * The default behavior of this method is to call setContentLength(int len) on the wrapped response object.
     */
    @Override
    public void setContentLength(int len) {
        this.response.setContentLength(len);
    }

    /**
     * The default behavior of this method is to call setContentLengthLong(long len) on the wrapped response object.
     *
     * @since Servlet 3.1
     */
    @Override
    public void setContentLengthLong(long len) {
        this.response.setContentLengthLong(len);
    }

    /**
     * The default behavior of this method is to call setContentType(String type) on the wrapped response object.
     */
    @Override
    public void setContentType(String type) {
        this.response.setContentType(type);
    }

    /**
     * The default behavior of this method is to return getContentType() on the wrapped response object.
     *
     * @since Servlet 2.4
     */
    @Override
    public String getContentType() {
        return this.response.getContentType();
    }

    /**
     * The default behavior of this method is to call setBufferSize(int size) on the wrapped response object.
     */
    @Override
    public void setBufferSize(int size) {
        this.response.setBufferSize(size);
    }

    /**
     * The default behavior of this method is to return getBufferSize() on the wrapped response object.
     */
    @Override
    public int getBufferSize() {
        return this.response.getBufferSize();
    }

    /**
     * The default behavior of this method is to call flushBuffer() on the wrapped response object.
     */
    @Override
    public void flushBuffer() throws IOException {
        this.response.flushBuffer();
    }

    /**
     * The default behavior of this method is to return isCommitted() on the wrapped response object.
     */
    @Override
    public boolean isCommitted() {
        return this.response.isCommitted();
    }

    /**
     * The default behavior of this method is to call reset() on the wrapped response object.
     */
    @Override
    public void reset() {
        this.response.reset();
    }

    /**
     * The default behavior of this method is to call resetBuffer() on the wrapped response object.
     */
    @Override
    public void resetBuffer() {
        this.response.resetBuffer();
    }

    /**
     * The default behavior of this method is to call setLocale(Locale loc) on the wrapped response object.
     */
    @Override
    public void setLocale(Locale loc) {
        this.response.setLocale(loc);
    }

    /**
     * The default behavior of this method is to return getLocale() on the wrapped response object.
     */
    @Override
    public Locale getLocale() {
        return this.response.getLocale();
    }

    /**
     * Checks (recursively) if this ServletResponseWrapper wraps the given {@link ServletResponse} instance.
     *
     * @param wrapped the ServletResponse instance to search for
     *
     * @return true if this ServletResponseWrapper wraps the given ServletResponse instance, false otherwise
     *
     * @since Servlet 3.0
     */
    public boolean isWrapperFor(ServletResponse wrapped) {
        if (response == wrapped) {
            return true;
        } else if (response instanceof ServletResponseWrapper) {
            return ((ServletResponseWrapper) response).isWrapperFor(wrapped);
        } else {
            return false;
        }
    }

    /**
     * Checks (recursively) if this ServletResponseWrapper wraps a {@link ServletResponse} of the given class type.
     *
     * @param wrappedType the ServletResponse class type to search for
     *
     * @return true if this ServletResponseWrapper wraps a ServletResponse of the given class type, false otherwise
     *
     * @throws IllegalArgumentException if the given class does not implement {@link ServletResponse}
     *
     * @since Servlet 3.0
     */
    public boolean isWrapperFor(Class<?> wrappedType) {
        if (!ServletResponse.class.isAssignableFrom(wrappedType)) {
            throw new IllegalArgumentException("Given class " + wrappedType.getName() + " not a subinterface of "
                    + ServletResponse.class.getName());
        }
        if (wrappedType.isAssignableFrom(response.getClass())) {
            return true;
        } else if (response instanceof ServletResponseWrapper) {
            return ((ServletResponseWrapper) response).isWrapperFor(wrappedType);
        } else {
            return false;
        }
    }

}