rest-assured/src/main/java/io/restassured/config/DecoderConfig.java
public DecoderConfig defaultCharsetForContentType(Charset charset, ContentType contentType) {
        notNull(charset, "Charset");
        return defaultCharsetForContentType(charset.toString(), contentType);
    }
public DecoderConfig defaultCharsetForContentType(Charset charset, ContentType contentType) {
        notNull(charset, "Charset");
        return defaultCharsetForContentType(charset.toString(), contentType);
    }
Specify the default charset to use for the specific content-type if it's not specified in the content-type header explicitly

@param charset     The charset to use as default (unless specified explicitly)
@param contentType The content-type
@return A new instance of {@link DecoderConfig}