概述
在servlet中設置response.setContentType（“application/json”）返回json格式數據類型時在ie瀏覽器中提示下載文件。這種現象是ie瀏覽不支持application/json數據格式引起的，只要在servlet中再填上一句response.setHeader("Content-Type", "text/html")就能解決問題（應爲瀏覽器對數據格式的識別靠的是響應頭裏面的Content-Type，所以，此種情況下頁面在處理返回數據的時候，要先利用js把文本格式轉化爲json格式：eval()函數可以實現此功能）。
（注意：有文章說，ie瀏覽器重ie10開始就開始支持application/json了，但是我親測過後並不是這個樣子，不說ie10，就連ie11也不支持，也有可能是我的瀏覽器問題）
乍一看response.setContentType（XX）和response.setHeader("Content-Type", XX)不是一樣的概念嗎，其實並不是這樣子的，前者設置返回的數據的類型，和瀏覽器沒多大關係（其實也有關係，在設置前者而不設置後者的情況下，後者的值默認爲前者，但是兩者確實是有本質的區別的），後者設置的是相應頭參數，響應頭中的Content-Type決定了瀏覽器以什麼方式來處理相應內容。
response.setContentType（“application/json”）：表示響應數據類型是json
response.setHeader("Content-Type",“application/json”):表示響應頭參數值
代碼檢驗
服務器端只設置response.setContentType，出現瀏覽器接收到服務器端返回的數據類型和響應頭Content-Type值都爲response.setContentType設置的值：
代碼:
package com.sends.test;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class TestServlet
*/
@WebServlet("/TestServlet")
public class TestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* Default constructor.
*/
public TestServlet() {
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("application/json");
response.setCharacterEncoding("utf-8");
//response.setHeader("Content-Type", "text/html");
PrintWriter writer = response.getWriter();
writer.write("{\"msg\":\"success\"}");
writer.flush();
writer.close();
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
瀏覽器效果:
服務器端同時設置response.setContentType("XXX")和response.setHeader("Content-Type"，"XXX"），瀏覽器顯示返回數據類型爲response.setContentType("XXX")設置值，響應頭值爲response.setHeader("Content-Type"，"XXX"）設置值：
代碼：
package com.sends.test;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class TestServlet
*/
@WebServlet("/TestServlet")
public class TestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* Default constructor.
*/
public TestServlet() {
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("application/json");
response.setCharacterEncoding("utf-8");
response.setHeader("Content-Type", "text/html");
PrintWriter writer = response.getWriter();
writer.write("{\"msg\":\"success\"}");
writer.flush();
writer.close();
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
瀏覽器效果：
ie瀏覽器就要設置爲此種情況程序才能正常工作：
爲了進一步驗證，來一個絕一點的例子，響應內容類型爲text/html,響應頭Content-Type參數值設置爲application/json。結果顯示，雖然響應內容爲text/html格式,ie瀏覽器仍舊提示下載文件。
代碼：
package com.sends.test;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class TestServlet
*/
@WebServlet("/TestServlet")
public class TestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* Default constructor.
*/
public TestServlet() {
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/html");
response.setCharacterEncoding("utf-8");
response.setHeader("Content-Type", "application/json");
PrintWriter writer = response.getWriter();
writer.write("{\"msg\":\"success\"}");
writer.flush();
writer.close();
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
ie效果：
更正：
通過同時反映，瞭解到以上描述是錯誤的，setHeader("Content-Type", "XXX")和setContentType("XXX")描述的是一樣的概念（https://github.com/apache/tomcat80/blob/trunk/java/org/apache/coyote/Response.java#L32），如果要ie瀏覽器裏面返回的數據不提示下載，只需要setContentType("text/html")就行了，然後在處理返回信息的時候先利用js把數據轉化爲想要的對象再進行處理。
