PropertyMockingApplicationContextInitializer.java

package org.mockserver.examples.web.controller;

import org.mockserver.socket.PortFactory;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.MutablePropertySources;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.mock.env.MockPropertySource;

public class PropertyMockingApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        MutablePropertySources propertySources = applicationContext.getEnvironment().getPropertySources();
        MockPropertySource mockEnvVars = new MockPropertySource().withProperty("bookService.port", PortFactory.findFreePort());
        propertySources.replace(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, mockEnvVars);
    }
}