juneau-core/juneau-marshall/src/main/java/org/apache/juneau/http/part/PartBeanMeta.java

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package org.apache.juneau.http.part;

import static org.apache.juneau.internal.ExceptionUtils.*;
import static org.apache.juneau.internal.StringUtils.*;

import java.lang.reflect.*;
import java.util.concurrent.*;

import org.apache.juneau.http.annotation.*;
import org.apache.juneau.httppart.*;
import org.apache.juneau.reflect.*;

/**
 * Holds metadata about http part beans (POJOs that get serialized as HTTP parts such as form data or query parameters).
 * {@review}
 *
 * <p>
 * HTTP part beans are typically annotated with {@link Query @Query}, {@link FormData @FormData}, or {@link Path @Path}
 * although it's not an absolute requirement.
 *
 * <p>
 * HTTP part beans must have one of the following public constructors:
 * <ul>
 * 	<li><c><jk>public</jk> X(String <jv>partValue</jv>)</c>
 * 	<li><c><jk>public</jk> X(Object <jv>partValue</jv>)</c>
 * 	<li><c><jk>public</jk> X(String <jv>partName</jv>, String <jv>partValue</jv>)</c>
 * 	<li><c><jk>public</jk> X(String <jv>partName</jv>, Object <jv>partValue</jv>)</c>
 * </ul>
 *
 * <p>
 * <h5 class='figure'>Example</h5>
 * <p class='bcode w800'>
 * 	<jc>// Our part bean.</jc>
 * 	<ja>@Query</ja>(<js>"foo"</js>)
 * 	<jk>public class</jk> FooPart <jk>extends</jk> BasicStringPart {
 *
 * 		<jk>public</jk> FooPart(String <jv>partValue</jv>) {
 * 			<jk>super</jk>(<js>"foo"</js>, <jv>partValue</jv>);
 * 		}
 *  }
 *
 *  <jc>// Code to retrieve a part bean from a part list in a request.</jc>
 *  PartList <jv>parts</jv> = <jv>httpRequest</jv>.getFormDataList();
 *  FooPart <jv>foo</jv> = <jv>parts</jv>.get(FooPart.<jk>class</jk>);
 * </p>
 *
 * @param <T> The HTTP part bean type.
 */
public class PartBeanMeta<T> {

	private static final ConcurrentHashMap<Class<?>,PartBeanMeta<?>> CACHE = new ConcurrentHashMap<>();

	private final Class<T> type;
	private final Constructor<T> constructor;
	private final HttpPartSchema schema;

	/**
	 * Finds the part bean meta for the specified type.
	 *
	 * @param type The part bean type.
	 * @return The metadata, or <jk>null</jk> if a valid constructor could not be found.
	 */
	@SuppressWarnings("unchecked")
	public static <T> PartBeanMeta<T> of(Class<T> type) {
		PartBeanMeta<?> m = CACHE.get(type);
		if (m == null) {
			m = new PartBeanMeta<>(type);
			CACHE.put(type, m);
		}
		return (PartBeanMeta<T>)m;
	}

	private PartBeanMeta(Class<T> type) {
		this.type = type;

		ClassInfo ci = ClassInfo.of(type);

		ConstructorInfo cci = ci.getPublicConstructor(String.class);
		if (cci == null)
			cci = ci.getPublicConstructor(Object.class);
		if (cci == null)
			cci = ci.getPublicConstructor(String.class, String.class);
		if (cci == null)
			cci = ci.getPublicConstructor(String.class, Object.class);
		constructor = cci == null ? null : cci.inner();

		if (ci.hasAnnotation(Query.class))
			this.schema = HttpPartSchema.create(Query.class, type);
		else if (ci.hasAnnotation(FormData.class))
			this.schema = HttpPartSchema.create(FormData.class, type);
		else if (ci.hasAnnotation(Path.class))
			this.schema = HttpPartSchema.create(Path.class, type);
		else if (ci.hasAnnotation(ResponseHeader.class))
			this.schema = HttpPartSchema.create(ResponseHeader.class, type);
		else
			this.schema = HttpPartSchema.create(org.apache.juneau.http.annotation.Header.class, type);
	}

	/**
	 * Returns schema information about this part.
	 *
	 * <p>
	 * This is information pulled from {@link Query @Query}, {@link FormData @FormData}, or {@link Path @Path} annotations
	 * on the class.
	 *
	 * @return The schema information.
	 */
	public HttpPartSchema getSchema() {
		return schema;
	}

	/**
	 * Constructs a part bean with the specified name or value.
	 *
	 * <p>
	 * Can only be used on beans where the part name is known.
	 *
	 * @param value
	 * 	The part value.
	 * @return A newly constructed bean.
	 */
	public T construct(Object value) {
		return construct(null, value);
	}

	/**
	 * Constructs a part bean with the specified name or value.
	 *
	 * @param name
	 * 	The part name.
	 * 	<br>If <jk>null</jk>, uses the value pulled from the {@link org.apache.juneau.http.annotation.Header#name() @Header(name)} or
	 * 	{@link org.apache.juneau.http.annotation.Header#value() @Header(value)} annotations.
	 * @param value
	 * 	The part value.
	 * @return A newly constructed bean.
	 * @throws UnsupportedOperationException If bean could not be constructed (e.g. couldn't find a constructor).
	 */
	public T construct(String name, Object value) {

		if (constructor == null)
			throw new UnsupportedOperationException("Constructor for type "+type.getName()+" could not be found.");

		if (name == null)
			name = schema.getName();

		Class<?>[] pt = constructor.getParameterTypes();
		Object[] args = new Object[pt.length];
		if (pt.length == 1) {
			args[0] = pt[0] == String.class ? stringify(value) : value;
		} else {
			if (name == null)
				throw new UnsupportedOperationException("Constructor for type "+type.getName()+" requires a name as the first argument.");
			args[0] = name;
			args[1] = pt[1] == String.class ? stringify(value) : value;
		}

		try {
			return constructor.newInstance(args);
		} catch (Exception e) {
			throw runtimeException(e);
		}
	}
}