JinjavaBeanELResolver.java

package com.hubspot.jinjava.el.ext;

import java.util.Set;

import javax.el.BeanELResolver;
import javax.el.ELContext;
import javax.el.MethodNotFoundException;

import com.google.common.base.CaseFormat;
import com.google.common.collect.ImmutableSet;

/**
 * {@link BeanELResolver} supporting snake case property names.
 */
public class JinjavaBeanELResolver extends BeanELResolver {
  private static final Set<String> RESTRICTED_PROPERTIES = ImmutableSet.<String> builder()
      .add("class")
      .build();

  private static final Set<String> RESTRICTED_METHODS = ImmutableSet.<String> builder()
      .add("clone")
      .add("hashCode")
      .add("notify")
      .add("notifyAll")
      .add("wait")
      .build();

  /**
   * Creates a new read/write {@link JinjavaBeanELResolver}.
   */
  public JinjavaBeanELResolver() {}

  /**
   * Creates a new {@link JinjavaBeanELResolver} whose read-only status is determined by the given parameter.
   */
  public JinjavaBeanELResolver(boolean readOnly) {
    super(readOnly);
  }

  @Override
  public Class<?> getType(ELContext context, Object base, Object property) {
    return super.getType(context, base, validatePropertyName(property));
  }

  @Override
  public Object getValue(ELContext context, Object base, Object property) {
    return super.getValue(context, base, validatePropertyName(property));
  }

  @Override
  public boolean isReadOnly(ELContext context, Object base, Object property) {
    return super.isReadOnly(context, base, validatePropertyName(property));
  }

  @Override
  public void setValue(ELContext context, Object base, Object property, Object value) {
    super.setValue(context, base, validatePropertyName(property), value);
  }

  @Override
  public Object invoke(ELContext context, Object base, Object method, Class<?>[] paramTypes, Object[] params) {
    if (method == null || RESTRICTED_METHODS.contains(method.toString())) {
      throw new MethodNotFoundException("Cannot find method '" + method + "' in " + base.getClass());
    }
    return super.invoke(context, base, method, paramTypes, params);
  }

  private String validatePropertyName(Object property) {
    String propertyName = transformPropertyName(property);

    if (RESTRICTED_PROPERTIES.contains(propertyName)) {
      return null;
    }

    return propertyName;
  }

  /**
   * Transform snake case to property name.
   */
  private String transformPropertyName(Object property) {
    if (property == null) {
      return null;
    }

    String propertyStr = property.toString();
    if (propertyStr.indexOf('_') == -1) {
      return propertyStr;
    }
    return CaseFormat.LOWER_UNDERSCORE.to(CaseFormat.LOWER_CAMEL, propertyStr);
  }

}