How to configure CharacterEncodingFilter in SpringBoot?

Since Spring Boot 1.4.2 registering your own CharacterEncodingFilter will work ONLY IF you disable Spring's own instance of this bean by setting spring.http.encoding.enabled=false in the application.properties.

However, one can resolve this matter without any Filter instantiation by adding these setting to the application.properties:

# Charset of HTTP requests and responses. Added to the "Content-Type" header if not set explicitly.
spring.http.encoding.charset=UTF-8
# Enable http encoding support.
spring.http.encoding.enabled=true
# Force the encoding to the configured charset on HTTP requests and responses.
spring.http.encoding.force=true

Source: Appendix A. Common application properties

Example code for your Application.java class, as proposed in the comments above:

@Bean
public FilterRegistrationBean filterRegistrationBean() {
    FilterRegistrationBean registrationBean = new FilterRegistrationBean();
    CharacterEncodingFilter characterEncodingFilter = new CharacterEncodingFilter();
    characterEncodingFilter.setForceEncoding(true);
    characterEncodingFilter.setEncoding("UTF-8");
    registrationBean.setFilter(characterEncodingFilter);
    return registrationBean;
}