java 后端返回文件url给前端 javaweb返回json

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技术领航员 2023-09-04 22:45:17

文章标签 java 后端返回文件url给前端 json 测试 javascript ViewUI 文章分类 Java 后端开发

Web项目中经常涉及到AJAX请求返回JSON和JSONP数据。JSON数据在server端和浏览器端传输，本质上就是传输字符串，只是这个字符串符合JSON语法格式。浏览器端会依照普通文本的格式接收JSON字符串。终于JSON字符串转成JSON对象通过JavaScript实现。眼下部分浏览器(IE9下面浏览器没有提供)和经常使用的JS库都提供了JSON序列化和反序列化的方法。如jQuery的AJAX请求能够指定返回的数据格式，包含text、json、jsonp、xml、html等。

Webserver端仅仅要把Java对象数据转成JSON字符串。并把JSON字符串以文本的形式通过response输出就可以。

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.serializer.SerializerFeature;

/**
 * 
 * Web服务端返回JSON工具类
 * 工具类依赖FastJSON
 * 工具类支持返回JSON和JSONP格式数据
 * @author accountwcx@qq.com
 * 
 */
public class ResponseJsonUtils {
	/**
	 * 默认字符编码
	 */
	private static String encoding = "UTF-8";
	
	/**
	 * JSONP默认的回调函数
	 */
	private static String callback = "callback";
	
	/**
	 * FastJSON的序列化设置
	 */
	private static SerializerFeature[] features =  new SerializerFeature[]{
		//输出Map中为Null的值
		SerializerFeature.WriteMapNullValue,
		
		//假设Boolean对象为Null。则输出为false
		SerializerFeature.WriteNullBooleanAsFalse,
		
		//假设List为Null。则输出为[]
		SerializerFeature.WriteNullListAsEmpty,
		
		//假设Number为Null。则输出为0
		SerializerFeature.WriteNullNumberAsZero,
		
		//输出Null字符串
		SerializerFeature.WriteNullStringAsEmpty,
		
		//格式化输出日期
		SerializerFeature.WriteDateUseDateFormat
	};
	
	/**
	 * 把Java对象JSON序列化
	 * @param obj 须要JSON序列化的Java对象
	 * @return JSON字符串
	 */
	private static String toJSONString(Object obj){
		return JSON.toJSONString(obj, features);
	}
	
	/**
	 * 返回JSON格式数据
	 * @param response
	 * @param data 待返回的Java对象
	 * @param encoding 返回JSON字符串的编码格式
	 */
	public static void json(HttpServletResponse response, Object data, String encoding){
		//设置编码格式
		response.setContentType("text/plain;charset=" + encoding);
		response.setCharacterEncoding(encoding);
		
		PrintWriter out = null;
		try{
			out = response.getWriter();
			out.write(toJSONString(data));
			out.flush();
		}catch(IOException e){
			e.printStackTrace();
		}
	}
	
	/**
	 * 返回JSON格式数据，使用默认编码
	 * @param response
	 * @param data 待返回的Java对象
	 */
	public static void json(HttpServletResponse response, Object data){
		json(response, data, encoding);
	}
	
	/**
	 * 返回JSONP数据，使用默认编码和默认回调函数
	 * @param response
	 * @param data JSONP数据
	 */
	public static void jsonp(HttpServletResponse response, Object data){
		jsonp(response, callback, data, encoding);
	}
	
	/**
	 * 返回JSONP数据，使用默认编码
	 * @param response
	 * @param callback JSONP回调函数名称
	 * @param data JSONP数据
	 */
	public static void jsonp(HttpServletResponse response, String callback, Object data){
		jsonp(response, callback, data, encoding);
	}
	
	/**
	 * 返回JSONP数据
	 * @param response
	 * @param callback JSONP回调函数名称
	 * @param data JSONP数据
	 * @param encoding JSONP数据编码
	 */
	public static void jsonp(HttpServletResponse response, String callback, Object data, String encoding){
		StringBuffer sb = new StringBuffer(callback);
		sb.append("(");
		sb.append(toJSONString(data));
		sb.append(");");

		// 设置编码格式
		response.setContentType("text/plain;charset=" + encoding);
		response.setCharacterEncoding(encoding);

		PrintWriter out = null;
		try {
			out = response.getWriter();
			out.write(sb.toString());
			out.flush();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public static String getEncoding() {
		return encoding;
	}

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

	public static String getCallback() {
		return callback;
	}

	public static void setCallback(String callback) {
		ResponseJsonUtils.callback = callback;
	}
}

/**
 * 在Servlet返回JSON数据
 */
@WebServlet("/json.do")
public class JsonServlet extends HttpServlet {
	private static final long serialVersionUID = 7500835936131982864L;

	/**
	 * 返回json格式数据
	 */
	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		ResponseJsonUtils.json(response, data);
	}
}

/**
 * Servlet返回JSONP格式数据
 */
@WebServlet("/jsonp.do")
public class JsonpServlet extends HttpServlet {
	private static final long serialVersionUID = -8343408864035108293L;

	/**
	 * 请求会发送callback參数作为回调函数，假设没有发送callback參数则使用默认回调函数
	 */
	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//client发送的回调函数
		String callback = request.getParameter("callback");
		
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		if(callback == null || callback.length() == 0){
			//假设client没有发送回调函数。则使用默认的回调函数
			ResponseJsonUtils.jsonp(response, data);
		}else{
			//使用client的回调函数
			ResponseJsonUtils.jsonp(response, callback, data);
		}
	}
}

/**
 * 在Struts2中返回JSON和JSONP
 */
public class JsonAction extends ActionSupport {
	private static final long serialVersionUID = 5391000845385666048L;
	
	/**
	 * JSONP的回调函数
	 */
	private String callback;
	
	/**
	 * 返回JSON
	 */
	public void json(){
		HttpServletResponse response = ServletActionContext.getResponse();
		
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		ResponseJsonUtils.json(response, data);
	}
	
	/**
	 * 返回JSONP
	 */
	public void jsonp(){
		HttpServletResponse response = ServletActionContext.getResponse();
		
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		if(callback == null || callback.length() == 0){
			//假设client没有发送回调函数，则使用默认的回调函数
			ResponseJsonUtils.jsonp(response, data);
		}else{
			//使用client的回调函数
			ResponseJsonUtils.jsonp(response, callback, data);
		}
	}

	public String getCallback() {
		return callback;
	}

	public void setCallback(String callback) {
		this.callback = callback;
	}
}

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * Spring MVC返回JSON和JSONP数据
 */
@Controller
@RequestMapping("/json")
public class JsonController {
	
	/**
	 * 返回JSON数据
	 * @param request
	 * @param response
	 */
	@RequestMapping("/json.do")
	public void json(HttpServletRequest request, HttpServletResponse response){
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		ResponseJsonUtils.json(response, data);
	}
	
	/**
	 * 返回JSONP数据
	 * @param callback JSONP的回调函数
	 * @param request
	 * @param response
	 */
	@RequestMapping("/jsonp.do")
	public void json(String callback, HttpServletRequest request, HttpServletResponse response){
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		if(callback == null || callback.length() == 0){
			//假设client没有发送回调函数，则使用默认的回调函数
			ResponseJsonUtils.jsonp(response, data);
		}else{
			//使用client的回调函数
			ResponseJsonUtils.jsonp(response, callback, data);
		}
	}
}

Webserver端仅仅要把Java对象数据转成JSON字符串。并把JSON字符串以文本的形式通过response输出就可以。

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.serializer.SerializerFeature;

/**
 * 
 * Web服务端返回JSON工具类
 * 工具类依赖FastJSON
 * 工具类支持返回JSON和JSONP格式数据
 * @author accountwcx@qq.com
 * 
 */
public class ResponseJsonUtils {
	/**
	 * 默认字符编码
	 */
	private static String encoding = "UTF-8";
	
	/**
	 * JSONP默认的回调函数
	 */
	private static String callback = "callback";
	
	/**
	 * FastJSON的序列化设置
	 */
	private static SerializerFeature[] features =  new SerializerFeature[]{
		//输出Map中为Null的值
		SerializerFeature.WriteMapNullValue,
		
		//假设Boolean对象为Null。则输出为false
		SerializerFeature.WriteNullBooleanAsFalse,
		
		//假设List为Null。则输出为[]
		SerializerFeature.WriteNullListAsEmpty,
		
		//假设Number为Null。则输出为0
		SerializerFeature.WriteNullNumberAsZero,
		
		//输出Null字符串
		SerializerFeature.WriteNullStringAsEmpty,
		
		//格式化输出日期
		SerializerFeature.WriteDateUseDateFormat
	};
	
	/**
	 * 把Java对象JSON序列化
	 * @param obj 须要JSON序列化的Java对象
	 * @return JSON字符串
	 */
	private static String toJSONString(Object obj){
		return JSON.toJSONString(obj, features);
	}
	
	/**
	 * 返回JSON格式数据
	 * @param response
	 * @param data 待返回的Java对象
	 * @param encoding 返回JSON字符串的编码格式
	 */
	public static void json(HttpServletResponse response, Object data, String encoding){
		//设置编码格式
		response.setContentType("text/plain;charset=" + encoding);
		response.setCharacterEncoding(encoding);
		
		PrintWriter out = null;
		try{
			out = response.getWriter();
			out.write(toJSONString(data));
			out.flush();
		}catch(IOException e){
			e.printStackTrace();
		}
	}
	
	/**
	 * 返回JSON格式数据，使用默认编码
	 * @param response
	 * @param data 待返回的Java对象
	 */
	public static void json(HttpServletResponse response, Object data){
		json(response, data, encoding);
	}
	
	/**
	 * 返回JSONP数据，使用默认编码和默认回调函数
	 * @param response
	 * @param data JSONP数据
	 */
	public static void jsonp(HttpServletResponse response, Object data){
		jsonp(response, callback, data, encoding);
	}
	
	/**
	 * 返回JSONP数据，使用默认编码
	 * @param response
	 * @param callback JSONP回调函数名称
	 * @param data JSONP数据
	 */
	public static void jsonp(HttpServletResponse response, String callback, Object data){
		jsonp(response, callback, data, encoding);
	}
	
	/**
	 * 返回JSONP数据
	 * @param response
	 * @param callback JSONP回调函数名称
	 * @param data JSONP数据
	 * @param encoding JSONP数据编码
	 */
	public static void jsonp(HttpServletResponse response, String callback, Object data, String encoding){
		StringBuffer sb = new StringBuffer(callback);
		sb.append("(");
		sb.append(toJSONString(data));
		sb.append(");");

		// 设置编码格式
		response.setContentType("text/plain;charset=" + encoding);
		response.setCharacterEncoding(encoding);

		PrintWriter out = null;
		try {
			out = response.getWriter();
			out.write(sb.toString());
			out.flush();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public static String getEncoding() {
		return encoding;
	}

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

	public static String getCallback() {
		return callback;
	}

	public static void setCallback(String callback) {
		ResponseJsonUtils.callback = callback;
	}
}

/**
 * 在Servlet返回JSON数据
 */
@WebServlet("/json.do")
public class JsonServlet extends HttpServlet {
	private static final long serialVersionUID = 7500835936131982864L;

	/**
	 * 返回json格式数据
	 */
	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		ResponseJsonUtils.json(response, data);
	}
}

/**
 * Servlet返回JSONP格式数据
 */
@WebServlet("/jsonp.do")
public class JsonpServlet extends HttpServlet {
	private static final long serialVersionUID = -8343408864035108293L;

	/**
	 * 请求会发送callback參数作为回调函数，假设没有发送callback參数则使用默认回调函数
	 */
	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//client发送的回调函数
		String callback = request.getParameter("callback");
		
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		if(callback == null || callback.length() == 0){
			//假设client没有发送回调函数。则使用默认的回调函数
			ResponseJsonUtils.jsonp(response, data);
		}else{
			//使用client的回调函数
			ResponseJsonUtils.jsonp(response, callback, data);
		}
	}
}

/**
 * 在Struts2中返回JSON和JSONP
 */
public class JsonAction extends ActionSupport {
	private static final long serialVersionUID = 5391000845385666048L;
	
	/**
	 * JSONP的回调函数
	 */
	private String callback;
	
	/**
	 * 返回JSON
	 */
	public void json(){
		HttpServletResponse response = ServletActionContext.getResponse();
		
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		ResponseJsonUtils.json(response, data);
	}
	
	/**
	 * 返回JSONP
	 */
	public void jsonp(){
		HttpServletResponse response = ServletActionContext.getResponse();
		
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		if(callback == null || callback.length() == 0){
			//假设client没有发送回调函数，则使用默认的回调函数
			ResponseJsonUtils.jsonp(response, data);
		}else{
			//使用client的回调函数
			ResponseJsonUtils.jsonp(response, callback, data);
		}
	}

	public String getCallback() {
		return callback;
	}

	public void setCallback(String callback) {
		this.callback = callback;
	}
}

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * Spring MVC返回JSON和JSONP数据
 */
@Controller
@RequestMapping("/json")
public class JsonController {
	
	/**
	 * 返回JSON数据
	 * @param request
	 * @param response
	 */
	@RequestMapping("/json.do")
	public void json(HttpServletRequest request, HttpServletResponse response){
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		ResponseJsonUtils.json(response, data);
	}
	
	/**
	 * 返回JSONP数据
	 * @param callback JSONP的回调函数
	 * @param request
	 * @param response
	 */
	@RequestMapping("/jsonp.do")
	public void json(String callback, HttpServletRequest request, HttpServletResponse response){
		Map<String, Object> data = new HashMap<String, Object>();
		
		data.put("date", new Date());
		data.put("email", "accountwcx@qq.com");
		data.put("age", 30);
		data.put("name", "csdn");
		data.put("array", new int[]{1,2,3,4});
		
		if(callback == null || callback.length() == 0){
			//假设client没有发送回调函数，则使用默认的回调函数
			ResponseJsonUtils.jsonp(response, data);
		}else{
			//使用client的回调函数
			ResponseJsonUtils.jsonp(response, callback, data);
		}
	}
}

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