StaticFieldConverterImpl.java

package org.springframework.roo.shell.converters;

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

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.Validate;
import org.springframework.roo.shell.Completion;
import org.springframework.roo.shell.Converter;
import org.springframework.roo.shell.MethodTarget;

/**
 * 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 {

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

  public void add(final Class<?> clazz) {
    Validate.notNull(clazz, "A class to provide conversion services is required");
    Validate.isTrue(fields.get(clazz) == null,
        "Class '%s' is already registered for completion services", clazz);
    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);
      }
    }
    Validate.notEmpty(ffields, "Zero public static fields accessible in '%s'", clazz);
    fields.put(clazz, ffields);
  }

  public Object convertFromText(final String value, final Class<?> requiredType,
      final String optionContext) {
    if (StringUtils.isBlank(value)) {
      return null;
    }
    final Map<String, Field> ffields = 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);
    }
  }

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

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

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