StaticFieldConverterImpl.java

package vnet.sms.common.shell.springshell.internal.converters;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import vnet.sms.common.shell.springshell.Completion;
import vnet.sms.common.shell.springshell.Converter;
import vnet.sms.common.shell.springshell.MethodTarget;
import vnet.sms.common.shell.springshell.internal.util.Assert;
import vnet.sms.common.shell.springshell.internal.util.StringUtils;

/**
 * A simple {@link Converter} for those classes which provide public static
 * fields to represent possible textual values.
 * 
 * @author Stefan Schmidt
 * @author Ben Alex
 * @since 1.0
 */
public class StaticFieldConverterImpl implements StaticFieldConverter {

	// Fields
	private final Map<Class<?>, Map<String, Field>>	fields	= new HashMap<Class<?>, Map<String, Field>>();

	@Override
	public void add(final Class<?> clazz) {
		Assert.notNull(clazz,
		        "A class to provide conversion services is required");
		Assert.isNull(this.fields.get(clazz), "Class '" + clazz
		        + "' is already registered for completion services");
		final Map<String, Field> ffields = new HashMap<String, Field>();
		for (final Field field : clazz.getFields()) {
			final int modifier = field.getModifiers();
			if (Modifier.isStatic(modifier) && Modifier.isPublic(modifier)) {
				ffields.put(field.getName(), field);
			}
		}
		Assert.notEmpty(ffields, "Zero public static fields accessible in '"
		        + clazz + "'");
		this.fields.put(clazz, ffields);
	}

	@Override
	public void remove(final Class<?> clazz) {
		Assert.notNull(clazz,
		        "A class that was providing conversion services is required");
		this.fields.remove(clazz);
	}

	@Override
	public Object convertFromText(final String value,
	        final Class<?> requiredType, final String optionContext) {
		if (StringUtils.isBlank(value)) {
			return null;
		}
		final Map<String, Field> ffields = this.fields.get(requiredType);
		if (ffields == null) {
			return null;
		}
		Field f = ffields.get(value);
		if (f == null) {
			// Fallback to case insensitive search
			for (final Field candidate : ffields.values()) {
				if (candidate.getName().equalsIgnoreCase(value)) {
					f = candidate;
					break;
				}
			}
			if (f == null) {
				// Still not found, despite a case-insensitive search
				return null;
			}
		}
		try {
			return f.get(null);
		} catch (final Exception ex) {
			throw new IllegalStateException("Unable to acquire field '" + value
			        + "' from '" + requiredType.getName() + "'", ex);
		}
	}

	@Override
	public boolean getAllPossibleValues(final List<Completion> completions,
	        final Class<?> requiredType, final String existingData,
	        final String optionContext, final MethodTarget target) {
		final Map<String, Field> ffields = this.fields.get(requiredType);
		if (ffields == null) {
			return true;
		}
		for (final String field : ffields.keySet()) {
			completions.add(new Completion(field));
		}
		return true;
	}

	@Override
	public boolean supports(final Class<?> requiredType,
	        final String optionContext) {
		return this.fields.get(requiredType) != null;
	}
}