Struts2-支持JSON

作者：聂勇 欢迎转载，请保留作者信息并说明文章来源！

• 工作环境（Runtime Enviroment）
• 实现步骤（Step By Step）
• 参考资料（Reference）

思路：通过Result将Action中指定的数据序列化成JSON。

工作环境（Runtime Enviroment）

• struts2-2.1.6
• json-lib-2.3-jdk15.jar
• flexjson-1.9.2.jar
• ezmorph-1.0.6.jar
• commons-lang-2.5.jar
• commons-collections-3.2.1.jar

实现步骤（Step By Step）

1、编写JSON Result类。

package cn.aofeng.common.util.json;

import java.io.OutputStream;
import javax.servlet.http.HttpServletResponse;
import net.sf.json.JSONObject;
import org.apache.log4j.Logger;
import org.apache.struts2.ServletActionContext;
import org.apache.struts2.StrutsException;
import org.apache.struts2.dispatcher.StrutsResultSupport;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;

/**
 * Struts2插件:JSON响应类型定义.
 *
 * @author aofeng
 */
public class JSONResult extends StrutsResultSupport {
    private static final Logger _logger = Logger.getLogger(JSONResult.class);
    
    private String jsonObjectProperty = "jsonObject";
    private String contentType = JSONSerializerUtils.JSON_MIME_TYPE;
    private String encoding = "UTF-8";
    
    public JSONResult() {
        
    }

    public String getJSONObjectProperty() {
        return jsonObjectProperty;
    }

    public void setJSONObjectProperty(String jsonObject) {
        jsonObjectProperty = jsonObject;
    }

    public String getContentType() {
        return contentType;
    }

    public void setContentType(String contentType) {
        this.contentType = contentType;
    }

    public String getEncoding() {
        return encoding;
    }

    public void setEncoding(String encoding) {
        this.encoding = encoding;
    }

    public void doExecute(String finalLocation, ActionInvocation invocation)
            throws Exception {
        JSONObject jsonObject = getJSONObject(invocation);
        if (jsonObject != null) {
            String json = jsonObject.toString();
            HttpServletResponse response = getServletResponse(invocation);
            response.setContentType(getContentType());
            response.setContentLength(json.getBytes(this.encoding).length);
            OutputStream os = response.getOutputStream();
            os.write(json.getBytes(this.encoding));
            os.flush();
        }
    }

    protected JSONObject getJSONObject(ActionInvocation invocation) {
        ActionContext actionContext = invocation.getInvocationContext();
        Object obj = actionContext.getValueStack().findValue(jsonObjectProperty);
        if (obj == null) {
            _logger.error("property [" + jsonObjectProperty + "] returns null, expecting JSONObject", new StrutsException("StrutsException"));
            return null;
        }
        if (!(JSONObject.class).isInstance(obj)) {
            _logger.error("property [" + jsonObjectProperty + "] is [" + obj + "] especting an instance of JSONObject", new StrutsException());
            return null;
        } else {
            return (JSONObject) obj;
        }
    }

    protected HttpServletResponse getServletResponse(ActionInvocation invocation) {
        return (HttpServletResponse) invocation.getInvocationContext().get(ServletActionContext.HTTP_RESPONSE);
    }

}

2、在Struts2中配置result type。

<result-types>
    <result-type name="json" class="cn.aofeng.common.util.json.JSONResult">
        <param name="jsonObjectProperty">jsonObject</param>
        <param name="contentType">application/json</param>
        <param name="encoding">UTF-8</param>
    </result-type>
</result-types>

3、在Action中返回JSON数据。
1）公共代码部分。

/**
 * 响应类型:JSON.
 */
protected final static String JSON = "json";
private JSONObject _jsonObject = new JSONObject();

public JSONObject getJsonObject() {
    return _jsonObject;
}

/**
 * 添加需转化成JSON的数据.
 *
 * @param key 键.
 * @param value 值.
 */
protected void putJsonElement(String key, Object value) {
    _jsonObject.put(key, value);
}

2）各Action实际应用部分示例。

public String execute() throws Exception {
    List<String> data = new ArrayList();
    data.add(something);    
    putJsonElemnt("dataList", data);
    
    return JSON;
}

参考资料（Reference）

1、http://struts.apache.org/2.0.14/struts2-core/apidocs/org/apache/struts2/dispatcher/StrutsResultSupport.html