Utility class to manually inject Value-Annotated fields for testing purposes

ValueInjectionUtils.java

package de.jangassen.spring.utils;

import java.lang.reflect.Field;
import java.util.Properties;

import org.apache.commons.lang3.reflect.FieldUtils;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.expression.MapAccessor;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.common.TemplateParserContext;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.SimpleEvaluationContext;
import org.springframework.util.PropertyPlaceholderHelper;
import org.springframework.util.SystemPropertyUtils;

public class ValueInjectionUtils {
  private static final ExpressionParser EXPRESSION_PARSER = new SpelExpressionParser();
  private static final ConversionService CONVERSION_SERVICE = new DefaultConversionService();
  private static final PropertyPlaceholderHelper PROPERTY_PLACEHOLDER_HELPER =
      new PropertyPlaceholderHelper(SystemPropertyUtils.PLACEHOLDER_PREFIX, SystemPropertyUtils.PLACEHOLDER_SUFFIX,
          SystemPropertyUtils.VALUE_SEPARATOR, true);

  public static void injectFieldValues(Object testClassInstance, Properties properties) {
    for (Field field : FieldUtils.getFieldsListWithAnnotation(testClassInstance.getClass(), Value.class)) {
      String value = field.getAnnotation(Value.class).value();
      if (value != null) {
        try {
          Object resolvedValue = resolveValue(value, properties);
          FieldUtils.writeField(field, testClassInstance, CONVERSION_SERVICE.convert(resolvedValue, field.getType()),
              true);
        } catch (IllegalAccessException e) {
          throw new IllegalStateException(e);
        }
      }
    }
  }

  private static Object resolveValue(String value, Properties properties) {
    String replacedPlaceholderString = PROPERTY_PLACEHOLDER_HELPER.replacePlaceholders(value, properties);
    return evaluateSpEL(replacedPlaceholderString, properties);
  }

  private static Object evaluateSpEL(String value, Properties properties) {
    Expression expression = EXPRESSION_PARSER.parseExpression(value, new TemplateParserContext());
    EvaluationContext context =
        SimpleEvaluationContext.forPropertyAccessors(new MapAccessor()).withRootObject(properties).build();
    return expression.getValue(context);
  }
}