SpringMVC返回JSON内容问题

最简单的直接用 @ResponseBody返回。
其二我经常使用的多视图，代码如下：
JsonView.java
package com.szfore.springmvc;
 
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.util.CollectionUtils;
import org.springframework.validation.BindingResult;
import org.springframework.web.servlet.view.AbstractView;
 
import com.google.gson.Gson;
/**
 * <b>function:</b>扩展AbstractView 实现JSON-lib视图
 * @author hoojo
 * @createDate 2011-4-28 下午05:26:43
 * @file MappingJsonlibVeiw.java
 * @package com.hoo.veiw.xml
 * @project SpringMVC4View
 * @blog http://blog.csdn.net/IBM_hoojo
 * @email hoojo_@126.com
 * @version 1.0
 */
public class JsonView extends AbstractView {
    public static final String DEFAULT_CONTENT_TYPE = "application/json";
    public static final String HTML_CONTENT_TYPE = "text/html";
    public static final String DEFAULT_CHAR_ENCODING = "UTF-8";
    private String encodeing = DEFAULT_CHAR_ENCODING;
     
    private Object jsonData = null;
    private Map<String, Object> _jsonDataMap = new HashMap<String, Object>();
     
    public void setEncodeing(String encodeing) {
        this.encodeing = encodeing;
    }
    private Set<String> renderedAttributes;
    public JsonView() {
        setContentType(DEFAULT_CONTENT_TYPE);
    }
    public JsonView(Object data) {
        setContentType(DEFAULT_CONTENT_TYPE);
        this.jsonData  =data;
    }
    @Override
    protected void renderMergedOutputModel(Map<String, Object> model, HttpServletRequest request,
            HttpServletResponse response) throws Exception {
        response.setCharacterEncoding(encodeing);
        response.setContentType(getContentType());
         
        PrintWriter out = response.getWriter();
        if(jsonData != null){
            out.print(new Gson().toJson(jsonData));
        }else if(!_jsonDataMap.isEmpty()){
            out.print(new Gson().toJson(_jsonDataMap));
        }else {
            model = filterModel(model);
            out.print(new Gson().toJson(model));
        }
    }
     
    /**
     * Filters out undesired attributes from the given model.
     * <p>Default implementation removes {@link BindingResult} instances and entries not included in the {@link
     * #setRenderedAttributes(Set) renderedAttributes} property.
     */
    protected Map<String, Object> filterModel(Map<String, Object> model) {
        Map<String, Object> result = new HashMap<String, Object>(model.size());
        Set<String> renderedAttributes =
                !CollectionUtils.isEmpty(this.renderedAttributes) ? this.renderedAttributes : model.keySet();
        for (Map.Entry<String, Object> entry : model.entrySet()) {
            if (!(entry.getValue() instanceof BindingResult) && renderedAttributes.contains(entry.getKey())) {
                result.put(entry.getKey(), entry.getValue());
            }
        }
 
        return result;
 
    }
     
    public void setJsonData(Object jsonData){
        this.jsonData = jsonData;
    }
     
    public static JsonView returnJson(Object jsonData){
        JsonView jsonView = new JsonView();
        jsonView.setJsonData(jsonData);
        return jsonView;
    }
     
    public JsonView put(String key, Object value)
    {
        _jsonDataMap.put(key, value);
        return this;
    }
}
MultiViewResover.java 
package com.szfore.springmvc;
 
import java.util.Locale;
import java.util.Map;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.ViewResolver;
 
/**
 * @author Jeson
 * @blog:http://www.gbsou.com
 * @date:Oct 20, 2009 8:39:27 AM
 * @version :1.0
 * 
 */
public class MultiViewResover implements ViewResolver {
 
    private Map<String, ViewResolver> resolvers;
     
    private final static String DEFAULT_RESOLVER = "jsp";
    private final static String JSON_RESOLVER = "json";
    private final static String JSON_VIEW_NAME = "jsonView";
     
    /*
     * 自定义resolve类默认为jsp视图，其余视图用下划线分隔
     */
    @Override
    public View resolveViewName(String viewName, Locale locale) throws Exception {
        //判断是否为json
        String tmpViewName = viewName.trim().toLowerCase();
        if(JSON_RESOLVER.equals(tmpViewName)){
            ViewResolver resolver = resolvers.get(JSON_RESOLVER);
            return resolver.resolveViewName(JSON_VIEW_NAME, locale);
        }
        //若无下划线，默认转向jsp视图
        int n = viewName.lastIndexOf("_"); 
        if (n == (-1)){
            ViewResolver resolver = resolvers.get(DEFAULT_RESOLVER);
            return resolver.resolveViewName(viewName, locale);
        }
        //有的话截取下划线后面的字符串 这里一般是jsp,ftl,vm与配置文件中的<entry key="ftl">的key匹配
        String suffix = viewName.substring(n + 1);
        // 根据下划线后面的字符串去获取托管的视图解析类对象
        ViewResolver resolver = resolvers.get(suffix);
        // 取下划线前面的部分 那时真正的资源名.比如我们要使用hello.jsp 那viewName就应该是hello_jsp
        viewName = viewName.substring(0, n);
        if (resolver != null){
            return resolver.resolveViewName(viewName, locale);
        }
        return null;
    }
 
    public Map<String, ViewResolver> getResolvers() {
        return resolvers;
    }
 
    public void setResolvers(Map<String, ViewResolver> resolvers) {
        this.resolvers = resolvers;
    }
}
xml配置 
<!-- 多视图 -->
    <bean name="jsonView" class="com.szfore.springmvc.JsonView">
    </bean>
    <bean id="viewResolver" class="com.szfore.springmvc.MultiViewResover">
        <property name="resolvers">
            <map>
                <entry key="jsp">
                    <bean
                        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
                        <property name="prefix" value="/" />
                        <property name="suffix" value=".jsp" />
                    </bean>
                </entry>
                <entry key="json">
                    <bean class="org.springframework.web.servlet.view.BeanNameViewResolver">
                    </bean>
                </entry>
            </map>
        </property>
    </bean>
使用方法： 
4
@RequestMapping("/test")
public JsonView test(){
  return new JsonView(new User());
}