JsonRender.java

/**
 * Copyright (c) 2011-2017, James Zhan 詹波 (jfinal@126.com).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.jfinal.render;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import com.jfinal.kit.JsonKit;

/**
 * JsonRender.
 * <p>
 * IE 不支持content type 为 application/json, 在 ajax 上传文件完成后返回 json时 IE 提示下载文件,<br>
 * 解决办法是使用： render(new JsonRender(params).forIE());
 */
public class JsonRender extends Render {
	
	/**
	 * It creates the extra attribute below while tomcat take SSL open.
	 * http://git.oschina.net/jfinal/jfinal/issues/10
	 */
	private static final Set<String> excludedAttrs = new HashSet<String>() {
		private static final long serialVersionUID = 9186138395157680676L;
		{
			add("javax.servlet.request.ssl_session");
			add("javax.servlet.request.ssl_session_id");
			add("javax.servlet.request.ssl_session_mgr");
			add("javax.servlet.request.key_size");
			add("javax.servlet.request.cipher_suite");
		}
	};
	
	/**
	 * 仅对无参 renderJson() 起作用
	 */
	public static void addExcludedAttrs(String... attrs) {
		if (attrs != null) {
			for (String attr : attrs) {
				excludedAttrs.add(attr);
			}
		}
	}
	
	public static void removeExcludedAttrs(String... attrs) {
		if (attrs != null) {
			for (String attr : attrs) {
				excludedAttrs.remove(attr);
			}
		}
	}
	
	public static void clearExcludedAttrs() {
		excludedAttrs.clear();
	}
	
	/**
	 * http://zh.wikipedia.org/zh/MIME
	 * 在wiki中查到: 尚未被接受为正式数据类型的subtype，可以使用x-开始的独立名称（例如application/x-gzip）
	 * 所以以下可能要改成 application/x-json
	 * 
	 * 通过使用firefox测试,struts2-json-plugin返回的是 application/json, 所以暂不改为 application/x-json
	 * 1: 官方的 MIME type为application/json, 见 http://en.wikipedia.org/wiki/MIME_type
	 * 2: IE 不支持 application/json, 在 ajax 上传文件完成后返回 json时 IE 提示下载文件
	 */
	private static final String contentType = "application/json; charset=" + getEncoding();
	private static final String contentTypeForIE = "text/html; charset=" + getEncoding();
	private boolean forIE = false;
	
	public JsonRender forIE() {
		forIE = true;
		return this;
	}
	
	private String jsonText;
	private String[] attrs;
	
	public JsonRender() {
		
	}
	
	@SuppressWarnings("serial")
	public JsonRender(final String key, final Object value) {
		if (key == null) {
			throw new IllegalArgumentException("The parameter key can not be null.");
		}
		this.jsonText = JsonKit.toJson(new HashMap<String, Object>(){{put(key, value);}});
	}
	
	public JsonRender(String[] attrs) {
		if (attrs == null) {
			throw new IllegalArgumentException("The parameter attrs can not be null.");
		}
		this.attrs = attrs;
	}
	
	public JsonRender(String jsonText) {
		if (jsonText == null) {
			// throw new IllegalArgumentException("The parameter jsonString can not be null.");
			this.jsonText = "null";
		} else {
			this.jsonText = jsonText;
		}
	}
	
	public JsonRender(Object object) {
		this.jsonText = JsonKit.toJson(object);
	}
	
	public void render() {
		if (jsonText == null) {
			buildJsonText();
		}
		
		PrintWriter writer = null;
		try {
			response.setHeader("Pragma", "no-cache");	// HTTP/1.0 caches might not implement Cache-Control and might only implement Pragma: no-cache
			response.setHeader("Cache-Control", "no-cache");
			response.setDateHeader("Expires", 0);
			
			response.setContentType(forIE ? contentTypeForIE : contentType);
			writer = response.getWriter();
	        writer.write(jsonText);
	        writer.flush();
		} catch (IOException e) {
			throw new RenderException(e);
		}
		finally {
			if (writer != null) {
				writer.close();
			}
		}
	}
	
	@SuppressWarnings({"rawtypes", "unchecked"})
	private void buildJsonText() {
		Map map = new HashMap();
		if (attrs != null) {
			for (String key : attrs) {
				map.put(key, request.getAttribute(key));
			}
		}
		else {
			for (Enumeration<String> attrs=request.getAttributeNames(); attrs.hasMoreElements();) {
				String key = attrs.nextElement();
				if (excludedAttrs.contains(key)) {
					continue;
				}
				
				Object value = request.getAttribute(key);
				map.put(key, value);
			}
		}
		
		this.jsonText = JsonKit.toJson(map);
	}
	
	public String[] getAttrs() {
		return attrs;
	}
	
	public String getJsonText() {
		return jsonText;
	}
	
	public Boolean getForIE() {
		return forIE;
	}
}