/*
 * Copyright 2002-2020 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.http.client;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.Proxy;
import java.net.URI;
import java.net.URL;
import java.net.URLConnection;

import org.springframework.core.task.AsyncListenableTaskExecutor;
import org.springframework.http.HttpMethod;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

ClientHttpRequestFactory implementation that uses standard JDK facilities. 
Author:
Arjen Poutsma, Juergen Hoeller
See Also:
HttpURLConnection
HttpComponentsClientHttpRequestFactory
Since:
3.0/**
 * {@link ClientHttpRequestFactory} implementation that uses standard JDK facilities.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 3.0
 * @see java.net.HttpURLConnection
 * @see HttpComponentsClientHttpRequestFactory
 */
@SuppressWarnings("deprecation")
public class SimpleClientHttpRequestFactory implements ClientHttpRequestFactory, AsyncClientHttpRequestFactory {

	private static final int DEFAULT_CHUNK_SIZE = 4096;


	@Nullable
	private Proxy proxy;

	private boolean bufferRequestBody = true;

	private int chunkSize = DEFAULT_CHUNK_SIZE;

	private int connectTimeout = -1;

	private int readTimeout = -1;

	private boolean outputStreaming = true;

	@Nullable
	private AsyncListenableTaskExecutor taskExecutor;


	
Set the Proxy to use for this request factory. /**
	 * Set the {@link Proxy} to use for this request factory.
	 */
	public void setProxy(Proxy proxy) {
		this.proxy = proxy;
	}

	
Indicate whether this request factory should buffer the request body internally. 
Default is true. When sending large amounts of data via POST or PUT, it is recommended to change this property to false, so as not to run out of memory. This will result in a ClientHttpRequest that either streams directly to the underlying HttpURLConnection (if the Content-Length is known in advance), or that will use "Chunked transfer encoding" (if the Content-Length is not known in advance). 
See Also:
setChunkSize(int)
HttpURLConnection.setFixedLengthStreamingMode(int)/**
	 * Indicate whether this request factory should buffer the
	 * {@linkplain ClientHttpRequest#getBody() request body} internally.
	 * <p>Default is {@code true}. When sending large amounts of data via POST or PUT,
	 * it is recommended to change this property to {@code false}, so as not to run
	 * out of memory. This will result in a {@link ClientHttpRequest} that either
	 * streams directly to the underlying {@link HttpURLConnection} (if the
	 * {@link org.springframework.http.HttpHeaders#getContentLength() Content-Length}
	 * is known in advance), or that will use "Chunked transfer encoding"
	 * (if the {@code Content-Length} is not known in advance).
	 * @see #setChunkSize(int)
	 * @see HttpURLConnection#setFixedLengthStreamingMode(int)
	 */
	public void setBufferRequestBody(boolean bufferRequestBody) {
		this.bufferRequestBody = bufferRequestBody;
	}

	
Set the number of bytes to write in each chunk when not buffering request
bodies locally.
Note that this parameter is only used when bufferRequestBody is set to false, and the Content-Length is not known in advance. 
See Also:
setBufferRequestBody(boolean)/**
	 * Set the number of bytes to write in each chunk when not buffering request
	 * bodies locally.
	 * <p>Note that this parameter is only used when
	 * {@link #setBufferRequestBody(boolean) bufferRequestBody} is set to {@code false},
	 * and the {@link org.springframework.http.HttpHeaders#getContentLength() Content-Length}
	 * is not known in advance.
	 * @see #setBufferRequestBody(boolean)
	 */
	public void setChunkSize(int chunkSize) {
		this.chunkSize = chunkSize;
	}

	
Set the underlying URLConnection's connect timeout (in milliseconds).
A timeout value of 0 specifies an infinite timeout.
Default is the system's default timeout.
See Also:
setConnectTimeout.setConnectTimeout(int)/**
	 * Set the underlying URLConnection's connect timeout (in milliseconds).
	 * A timeout value of 0 specifies an infinite timeout.
	 * <p>Default is the system's default timeout.
	 * @see URLConnection#setConnectTimeout(int)
	 */
	public void setConnectTimeout(int connectTimeout) {
		this.connectTimeout = connectTimeout;
	}

	
Set the underlying URLConnection's read timeout (in milliseconds).
A timeout value of 0 specifies an infinite timeout.
Default is the system's default timeout.
See Also:
setReadTimeout.setReadTimeout(int)/**
	 * Set the underlying URLConnection's read timeout (in milliseconds).
	 * A timeout value of 0 specifies an infinite timeout.
	 * <p>Default is the system's default timeout.
	 * @see URLConnection#setReadTimeout(int)
	 */
	public void setReadTimeout(int readTimeout) {
		this.readTimeout = readTimeout;
	}

	
Set if the underlying URLConnection can be set to 'output streaming' mode. Default is true. 
When output streaming is enabled, authentication and redirection cannot be handled automatically. If output streaming is disabled, the HttpURLConnection.setFixedLengthStreamingMode and HttpURLConnection.setChunkedStreamingMode methods of the underlying connection will never be called. 
Params:
outputStreaming – if output streaming is enabled/**
	 * Set if the underlying URLConnection can be set to 'output streaming' mode.
	 * Default is {@code true}.
	 * <p>When output streaming is enabled, authentication and redirection cannot be handled automatically.
	 * If output streaming is disabled, the {@link HttpURLConnection#setFixedLengthStreamingMode} and
	 * {@link HttpURLConnection#setChunkedStreamingMode} methods of the underlying connection will never
	 * be called.
	 * @param outputStreaming if output streaming is enabled
	 */
	public void setOutputStreaming(boolean outputStreaming) {
		this.outputStreaming = outputStreaming;
	}

	
Set the task executor for this request factory. Setting this property is required for creating asynchronous requests. 
Params:
taskExecutor – the task executor/**
	 * Set the task executor for this request factory. Setting this property is required
	 * for {@linkplain #createAsyncRequest(URI, HttpMethod) creating asynchronous requests}.
	 * @param taskExecutor the task executor
	 */
	public void setTaskExecutor(AsyncListenableTaskExecutor taskExecutor) {
		this.taskExecutor = taskExecutor;
	}


	@Override
	public ClientHttpRequest createRequest(URI uri, HttpMethod httpMethod) throws IOException {
		HttpURLConnection connection = openConnection(uri.toURL(), this.proxy);
		prepareConnection(connection, httpMethod.name());

		if (this.bufferRequestBody) {
			return new SimpleBufferingClientHttpRequest(connection, this.outputStreaming);
		}
		else {
			return new SimpleStreamingClientHttpRequest(connection, this.chunkSize, this.outputStreaming);
		}
	}

	
{@inheritDoc}
Setting the taskExecutor property is required before calling this method. /**
	 * {@inheritDoc}
	 * <p>Setting the {@link #setTaskExecutor taskExecutor} property is required before calling this method.
	 */
	@Override
	public AsyncClientHttpRequest createAsyncRequest(URI uri, HttpMethod httpMethod) throws IOException {
		Assert.state(this.taskExecutor != null, "Asynchronous execution requires TaskExecutor to be set");

		HttpURLConnection connection = openConnection(uri.toURL(), this.proxy);
		prepareConnection(connection, httpMethod.name());

		if (this.bufferRequestBody) {
			return new SimpleBufferingAsyncClientHttpRequest(
					connection, this.outputStreaming, this.taskExecutor);
		}
		else {
			return new SimpleStreamingAsyncClientHttpRequest(
					connection, this.chunkSize, this.outputStreaming, this.taskExecutor);
		}
	}

	
Opens and returns a connection to the given URL.
The default implementation uses the given proxy - if any - to open a connection. 
Params:
url – the URL to open a connection to
proxy – the proxy to use, may be null
Throws:
IOException – in case of I/O errors
Returns:
the opened connection/**
	 * Opens and returns a connection to the given URL.
	 * <p>The default implementation uses the given {@linkplain #setProxy(java.net.Proxy) proxy} -
	 * if any - to open a connection.
	 * @param url the URL to open a connection to
	 * @param proxy the proxy to use, may be {@code null}
	 * @return the opened connection
	 * @throws IOException in case of I/O errors
	 */
	protected HttpURLConnection openConnection(URL url, @Nullable Proxy proxy) throws IOException {
		URLConnection urlConnection = (proxy != null ? url.openConnection(proxy) : url.openConnection());
		if (!(urlConnection instanceof HttpURLConnection)) {
			throw new IllegalStateException(
					"HttpURLConnection required for [" + url + "] but got: " + urlConnection);
		}
		return (HttpURLConnection) urlConnection;
	}

	
Template method for preparing the given HttpURLConnection. 
The default implementation prepares the connection for input and output, and sets the HTTP method.
Params:
connection – the connection to prepare
httpMethod – the HTTP request method (GET, POST, etc.)
Throws:
IOException – in case of I/O errors/**
	 * Template method for preparing the given {@link HttpURLConnection}.
	 * <p>The default implementation prepares the connection for input and output, and sets the HTTP method.
	 * @param connection the connection to prepare
	 * @param httpMethod the HTTP request method ({@code GET}, {@code POST}, etc.)
	 * @throws IOException in case of I/O errors
	 */
	protected void prepareConnection(HttpURLConnection connection, String httpMethod) throws IOException {
		if (this.connectTimeout >= 0) {
			connection.setConnectTimeout(this.connectTimeout);
		}
		if (this.readTimeout >= 0) {
			connection.setReadTimeout(this.readTimeout);
		}

		boolean mayWrite =
				("POST".equals(httpMethod) || "PUT".equals(httpMethod) ||
						"PATCH".equals(httpMethod) || "DELETE".equals(httpMethod));

		connection.setDoInput(true);
		connection.setInstanceFollowRedirects("GET".equals(httpMethod));
		connection.setDoOutput(mayWrite);
		connection.setRequestMethod(httpMethod);
	}

}