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019
020package org.apache.james.mime4j.stream;
021
022import org.apache.james.mime4j.MimeException;
023
024/**
025 * Body descriptor builders are intended to construct {@link BodyDescriptor} instances from
026 * multiple unstructured {@link RawField}s.
027 * <p/>
028 * Body descriptor builders are stateful and modal as they have to store intermediate results
029 * between method invocations and also rely on a particular sequence of method invocations
030 * (the mode of operation).
031 * <p/>
032 * Consumers are expected to interact with body descriptor builders in the following way:
033 * <ul>
034 * <li>Invoke {@link #reset()} method in order to reset builder's internal state and make it
035 *   ready to start the process of building a new {@link BodyDescriptor}.</li>
036 * <li>Invoke {@link #addField(RawField)} multiple times method in order to collect
037 *   necessary details for building a body descriptor. The builder can optionally
038 *   transform the unstructured field given an an input into a structured one and return
039 *   an instance {@link Field} that also implements a richer interface for a particular type
040 *   of fields such as <code>Content-Type</code>. The builder can also return <code>null</code>
041 *   if the field is to be ignored</li>
042 * <li>Optionally invoke {@link #newChild()} for each embedded body of content. Please note that
043 *   the resultant {@link BodyDescriptorBuilder}} child instance can inherit some its parent
044 *   properties such as MIME type.</li>
045 * <li>Invoke {@link #build()()} method in order to generate a {@link BodyDescriptor}} instance
046 *   based on the internal state of the builder.</li>
047 * </ul>
048 */
049public interface BodyDescriptorBuilder {
050
051    /**
052     * Resets the internal state of the builder making it ready to process new input.
053     */
054    void reset();
055
056    /**
057     * Updates builder's internal state by adding a new field. The builder can optionally
058     * transform the unstructured field given an an input into a structured one and return
059     * an instance {@link Field} that also implements a richer interface for a particular type
060     * of fields such as <code>Content-Type</code>. The builder can also return <code>null</code>
061     * if the field is to be ignored.
062     */
063    Field addField(RawField field) throws MimeException;
064
065    /**
066     * Builds an instance of {@link BodyDescriptor} based on the internal state.
067     */
068    BodyDescriptor build();
069
070    /**
071     * Creates an instance of {@link BodyDescriptorBuilder} to be used for processing of an
072     * embedded content body. Please the child instance can inherit some of its parent properties
073     * such as MIME type.
074     */
075    BodyDescriptorBuilder newChild();
076
077}