FormEncodingBuilder + set charset set media type

FormEncodingBuilderEx.java

/*
 * Copyright (C) 2014 Square, Inc.
 *
 * 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.
 */
/*
 * Copyright (C) 2015 daneko.
 *
 * 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 com.squareup.okhttp;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.nio.charset.Charset;
import java.util.Objects;

import com.squareup.okhttp.internal.Util;

//@formatter:off
/**
 * base on {@link com.squareup.okhttp.FormEncodingBuilder}
 * this is enabled to set charset and media_type
 * 
 * sample
 * <pre>
 * {@code
 * RequestBody sjisBody = new FormEncodingBuilderEx(Charset.formName("SJIS"))
 *   .add(...)
 *   .add(...)
 *   .build();
 * }
 * </pre>
 */
//@formatter:on
public final class FormEncodingBuilderEx {
    private static final MediaType DEFAULT_CONTENT_TYPE
            = MediaType.parse("application/x-www-form-urlencoded");

    private final StringBuilder content = new StringBuilder();

    private final Charset charset;
    private final MediaType contentType;

    public FormEncodingBuilderEx(final Charset charset, final MediaType mediaType) {
        this.charset = charset;
        if (!Objects.equals(mediaType.charset(), charset)) {
            this.contentType = MediaType.parse(String.format(
                    "%s/%s; charset=%s",
                    mediaType.type(),
                    mediaType.subtype(),
                    charset.displayName().toLowerCase()));
        } else {
            this.contentType = mediaType;
        }
    }

    public FormEncodingBuilderEx() {
        this(Util.UTF_8, DEFAULT_CONTENT_TYPE);
    }

    public FormEncodingBuilderEx(final Charset charset) {
        this(charset, DEFAULT_CONTENT_TYPE);
    }

    private String getEncodeType() {
        return this.charset.displayName();
    }

    /**
     * Add new key-value pair.
     */
    public FormEncodingBuilderEx add(String name, String value) {
        if (content.length() > 0) {
            content.append('&');
        }
        try {
            content.append(URLEncoder.encode(name, getEncodeType()))
                    .append('=')
                    .append(URLEncoder.encode(value, getEncodeType()));
        } catch (UnsupportedEncodingException e) {
            throw new AssertionError(e);
        }
        return this;
    }

    public RequestBody build() {
        if (content.length() == 0) {
            throw new IllegalStateException("Form encoded body must have at least one part.");
        }

        // Convert to bytes so RequestBody.create() doesn't add a charset to the content-type.
        byte[] contentBytes = content.toString().getBytes(charset);
        return RequestBody.create(contentType, contentBytes);
    }
}