tonivade.fixtures.json.JsonFixturesTestRule.java Source code

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Here is the source code for tonivade.fixtures.json.JsonFixturesTestRule.java

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/*
 * Copyright (c) 2015, Antonio Gabriel Muoz Conejo <antoniogmc at gmail dot com>
 * Distributed under the terms of the MIT License
 */
package tonivade.fixtures.json;

import static java.util.Objects.requireNonNull;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Collection;
import java.util.Map;
import java.util.stream.Stream;

import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;

public class JsonFixturesTestRule implements TestRule {

    private Object underTest;

    private Gson gson = new GsonBuilder().create();

    public JsonFixturesTestRule(Object underTest) {
        this.underTest = requireNonNull(underTest);
    }

    @Override
    public Statement apply(Statement base, Description description) {
        return new Statement() {
            @Override
            public void evaluate() throws Throwable {
                loadFixtures();
                base.evaluate();
            }
        };
    }

    private void loadFixtures() {
        Stream.of(underTest.getClass().getDeclaredFields()).filter(this::isJsonFixture).forEach(this::loadFixture);
    }

    private boolean isJsonFixture(Field field) {
        return field.isAnnotationPresent(JsonFixture.class);
    }

    private void loadFixture(Field field) {
        JsonFixture annotation = field.getAnnotation(JsonFixture.class);
        InputStream input = loadJsonFile(annotation.value());
        Object value = loadValue(input, field.getType(), field.getGenericType());
        setValue(field, value);
    }

    private InputStream loadJsonFile(String name) {
        return underTest.getClass().getResourceAsStream(requireNonNull(name));
    }

    private Object loadValue(InputStream input, Class<?> type, Type genericType) {
        return gson.fromJson(new InputStreamReader(requireNonNull(input)), getType(type, genericType));
    }

    private Type getType(Class<?> type, Type genericType) {
        Type realType = type;
        if (genericType instanceof ParameterizedType) {
            if (Collection.class.isAssignableFrom(type)) {
                realType = genericType;
            } else if (Map.class.isAssignableFrom(type)) {
                realType = genericType;
            }
        }
        return TypeToken.get(realType).getType();
    }

    private void setValue(Field field, Object value) {
        try {
            field.set(underTest, value);
        } catch (IllegalAccessException e) {
            throw new JsonFixtureException(field.getName());
        }
    }
}