在spring boot中配置：

@configuration
public class WebMvcConfigurer extends WebMvcConfigurerAdapter
{

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters)
{
    converters.add(new FastJsonHttpMessageConverter());
    super.configureMessageConverters(converters);
}

}

在controller中：

@GetMapping("/api/test")
public String test()
{
    String callback = "callback";
    String script = "<script type=\"text/javascript\">\n"
            + "window.top.window['" + callback + "']({success:true});\n"
            + "</script>";
    LOG.error("jsonp : " + script);
    return script;
}

这个输出的script是这样的：

"\u003Cscript type="text/javascript"\u003E\nwindow.top.window['callback']\u0028{success:true}\u0029;\n\u003C/script\u003E"