blocks|key|1367040|text|我完全按照您的建议做(返回一个String)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1367041|不过，您可以考虑设置MIME类型，以指示将返回JSON+(根据this+other+stackoverflow+post，它是“应用程序/json”)。|1367042|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/477816/the-right-json-content-type^0|F|6|0|V|T|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@$9|T|A|U|1|V]]|E|$]]|$1|H|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

I do exactly what you suggest (return a <code>String</code>).

You might consider setting the MIME type to indicate you're returning JSON, though (according to <a href="https://stackoverflow.com/questions/477816/the-right-json-content-type">this other stackoverflow post</a> it's "application/json").

blocks|key|1367104|text|为了方便Java编码，可能会有一个JSON对象。但最终数据结构将被序列化为字符串。设置一个合适的MIME类型会更好。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1367105|我推荐来自json.org的JSON+Java。|offset|length|1367106|entityMap|0|LINK|mutability|MUTABLE|url|http://www.json.org/|1|http://www.json.org/java/^0|0|5|8|0|E|9|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@$D|R|E|S|1|T]|$D|U|E|V|1|W]]|A|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]|N|$5|I|J|K|A|$L|O]]]]

There might be a JSON object for Java coding convenience. But at last the data structure will be serialized to string. Setting a proper MIME type would be nice.

I'd suggest <a href="http://www.json.org/java/" rel="nofollow noreferrer">JSON Java</a> from <a href="http://www.json.org/" rel="nofollow noreferrer">json.org</a>.

blocks|key|1367142|text|response.setContentType("text/json")；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1367143|//创建JSON字符串，我建议使用一些框架。|1367144|String+your_string；|1367145|out.write(your_string.getBytes("UTF-8"))；|1367146|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

response.setContentType("text/json");

//create the JSON string, I suggest using some framework.

String your_string;

out.write(your_string.getBytes("UTF-8"));

blocks|key|1152069|text|将JSON对象写入响应对象的输出流。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1152070|您还应按如下方式设置内容类型，这将指定您要返回的内容：|1152071|response.setContentType("application/json");
//+Get+the+printwriter+object+from+response+to+write+the+required+json+object+to+the+output+stream++++++
PrintWriter+out+=+response.getWriter();
//+Assuming+your+json+object+is+**jsonObject**,+perform+the+following,+it+will+return+your+json+object++
out.print(jsonObject);
out.flush();|code-block|syntax|javascript|1152072|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Write the JSON object to the response object's output stream.

You should also set the content type as follows, which will specify what you are returning: 

<pre><code>response.setContentType("application/json");
// Get the printwriter object from response to write the required json object to the output stream 
PrintWriter out = response.getWriter();
// Assuming your json object is **jsonObject**, perform the following, it will return your json object 
out.print(jsonObject);
out.flush();
</code></pre>

blocks|key|1152126|text|我使用Jackson将Java+Object转换为JSON+string，并按如下方式发送。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1152127|PrintWriter+out+=+response.getWriter();
ObjectMapper+objectMapper=+new+ObjectMapper();
String+jsonString+=+objectMapper.writeValueAsString(MyObject);
response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
out.print(jsonString);
out.flush();|code-block|syntax|javascript|1152128|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/FasterXML/jackson^0|3|7|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

I used <a href="https://github.com/FasterXML/jackson" rel="noreferrer">Jackson</a> to convert Java Object to JSON string and send as follows.

<pre><code>PrintWriter out = response.getWriter();
ObjectMapper objectMapper= new ObjectMapper();
String jsonString = objectMapper.writeValueAsString(MyObject);
response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
out.print(jsonString);
out.flush();
</code></pre>

blocks|key|1152164|text|取决于Java版本(或JDK、SDK、JRE...我不知道，我是Java生态系统的新手)，JsonObject是抽象的。因此，这是一个新的实现：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1152165|import+javax.json.Json;
import+javax.json.JsonObject;

...

try+(PrintWriter+out+=+response.getWriter())+{
++++response.setContentType("application/json");+++++++
++++response.setCharacterEncoding("UTF-8");

++++JsonObject+json+=+Json.createObjectBuilder().add("foo",+"bar").build();

++++out.print(json.toString());
}|code-block|syntax|javascript|1152166|entityMap^0|19|A|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Depending on the Java version (or JDK, SDK, JRE... i dunno, im new to the Java ecosystem), the <code>JsonObject</code> is abstract. So, this is a new implementation:

<pre><code>import javax.json.Json;
import javax.json.JsonObject;

...

try (PrintWriter out = response.getWriter()) {
 response.setContentType("application/json"); 
 response.setCharacterEncoding("UTF-8");

 JsonObject json = Json.createObjectBuilder().add("foo", "bar").build();

 out.print(json.toString());
}
</code></pre>

blocks|key|1152193|text|通过使用Gson，您可以发送json响应(请参阅以下代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1152194|你可以看到下面的代码|1152195|@WebServlet(urlPatterns+=+{"/jsonResponse"})
public+class+JsonResponse+extends+HttpServlet+{

@Override
protected+void+doGet(HttpServletRequest+request,+HttpServletResponse+response)
++++++++throws+ServletException,+IOException+{
++++response.setContentType("application/json");
++++response.setCharacterEncoding("utf-8");
++++Student+student+=+new+Student(12,+"Ram+Kumar",+"Male",+"1234565678");
++++Subject+subject1+=+new+Subject(1,+"Computer+Fundamentals");
++++Subject+subject2+=+new+Subject(2,+"Computer+Graphics");
++++Subject+subject3+=+new+Subject(3,+"Data+Structures");
++++Set+subjects+=+new+HashSet();
++++subjects.add(subject1);
++++subjects.add(subject2);
++++subjects.add(subject3);
++++student.setSubjects(subjects);
++++Address+address+=+new+Address(1,+"Street+23+NN+West+",+"Bhilai",+"Chhattisgarh",+"India");
++++student.setAddress(address);
++++Gson+gson+=+new+Gson();
++++String+jsonData+=+gson.toJson(student);
++++PrintWriter+out+=+response.getWriter();
++++try+{
++++++++out.println(jsonData);
++++}+finally+{
++++++++out.close();
++++}

++}
}|code-block|syntax|javascript|1152196|来自json+response+from+servlet+in+java的帮助|offset|length|1152197|entityMap|0|LINK|mutability|MUTABLE|url|https://www.ebhor.com/servlet-json-response/^0|0|0|0|2|Y|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@$K|Y|L|Z|1|10]]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

By Using Gson you can send json response see below code

You can see this code

<pre><code>@WebServlet(urlPatterns = {"/jsonResponse"})
public class JsonResponse extends HttpServlet {

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 response.setContentType("application/json");
 response.setCharacterEncoding("utf-8");
 Student student = new Student(12, "Ram Kumar", "Male", "1234565678");
 Subject subject1 = new Subject(1, "Computer Fundamentals");
 Subject subject2 = new Subject(2, "Computer Graphics");
 Subject subject3 = new Subject(3, "Data Structures");
 Set subjects = new HashSet();
 subjects.add(subject1);
 subjects.add(subject2);
 subjects.add(subject3);
 student.setSubjects(subjects);
 Address address = new Address(1, "Street 23 NN West ", "Bhilai", "Chhattisgarh", "India");
 student.setAddress(address);
 Gson gson = new Gson();
 String jsonData = gson.toJson(student);
 PrintWriter out = response.getWriter();
 try {
 out.println(jsonData);
 } finally {
 out.close();
 }

 }
}
</code></pre>

helpful from <a href="https://www.ebhor.com/servlet-json-response/" rel="nofollow noreferrer">json response from servlet in java</a>

How do you return a JSON object form a Java servlet.

Previously when doing AJAX with a servlet I have returned a string. Is there a JSON object type that needs to be used, or do you just return a String that looks like a JSON object e.g. 

<pre><code>String objectToReturn = "{ key1: 'value1', key2: 'value2' }";
</code></pre>

How do you return a JSON object from a Java Servlet

如何从Java servlet返回JSON对象。以前，在使用servlet执行AJAX时，我返回了一个字符串。是否有需要使用的JSON对象类型，或者只返回一个看起来像JSON对象的字符串，例如String objectToReturn = "{ key1: 'value1', key2: 'value2' }";

问如何从Java Servlet返回JSON对象
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