<script type="text/javascript">
$.ajax({
    type: "POST",
    url: "/pages/ajax",
    data: "name=garfield&age=18",
    success: function(data){
      console.log(data);
   }
  })
</script>

@ResponseBody
@RequestMapping("/ajax")
public String ajaxCharacter(){
  return "测试";
}

<filter>
  <filter-name>characterEncodingFilter</filter-name>
  <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
  <init-param><!-- 针对request -->
    <param-name>encoding</param-name>
    <param-value>UTF-8</param-value>
  </init-param>
  <init-param><!-- 针对response --> 
    <param-name>forceEncoding</param-name>
    <param-value>true</param-value>
  </init-param>
</filter>

public class StringHttpMessageConverter extends AbstractHttpMessageConverter<String> {
  public static final Charset DEFAULT_CHARSET = Charset.forName("ISO-8859-1");
  private final Charset defaultCharset;
  private final List<Charset> availableCharsets;
  private boolean writeAcceptCharset;

  protected void writeInternal(String s, HttpOutputMessage outputMessage)
      throws IOException {
    if (this.writeAcceptCharset) {
      outputMessage.getHeaders().setAcceptCharset(getAcceptedCharsets());
    }
    Charset charset = getContentTypeCharset(outputMessage.getHeaders()
        .getContentType());
    StreamUtils.copy(s, charset, outputMessage.getBody());
  }

  ...
}

public abstract class AbstractHttpMessageConverter<T> implements
    HttpMessageConverter<T> {
  protected final Log logger = LogFactory.getLog(super.getClass());

  private List<MediaType> supportedMediaTypes = Collections.emptyList();

  ...
}

@RequestMapping(value = “/test”,produces=”text/html;charset=UTF-8;”)

<mvc:annotation-driven>
  <mvc:message-converters register-defaults="true"> 
   <bean class="org.springframework.http.converter.StringHttpMessageConverter"> 
    <property name="supportedMediaTypes" value="text/html;charset=UTF-8"/> 
   </bean> 
  </mvc:message-converters> 
</mvc:annotation-driven>

@RequestMapping("/ajax")
public void ajaxCharacter(HttpServletResponse response) throws IOException{
  PrintWriter out = response.getWriter();
  out.print("测试");
  out.close();
}