blocks|key|594281|text|一个疯狂的想法，试着解析它并捕获异常：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|594282|import+org.json.*;

public+boolean+isJSONValid(String+test)+{
++++try+{
++++++++new+JSONObject(test);
++++}+catch+(JSONException+ex)+{
++++++++//+edited,+to+include+@Arthur's+comment
++++++++//+e.g.+in+case+JSONArray+is+valid+as+well...
++++++++try+{
++++++++++++new+JSONArray(test);
++++++++}+catch+(JSONException+ex1)+{
++++++++++++return+false;
++++++++}
++++}
++++return+true;
}|code-block|syntax|javascript|594283|这段代码使用org.json+JSON+API实现，可以使用on+github、in+maven和部分on+Android。|offset|length|594284|entityMap|0|LINK|mutability|MUTABLE|url|https://www.json.org/|1|https://github.com/stleary/JSON-java|2|http://mvnrepository.com/artifact/org.json/json|3|https://developer.android.com/reference/org/json/package-summary.html^0|0|0|6|8|0|U|9|1|14|8|2|1F|A|3|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@]|9|@$I|11|J|12|1|13]|$I|14|J|15|1|16]|$I|17|J|18|1|19]|$I|1A|J|1B|1|1C]]|A|$]]|$1|K|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]|S|$5|N|O|P|A|$Q|T]]|U|$5|N|O|P|A|$Q|V]]|W|$5|N|O|P|A|$Q|X]]]]

A wild idea, try parsing it and catch the exception:
<pre><code>import org.json.*;

public boolean isJSONValid(String test) {
 try {
 new JSONObject(test);
 } catch (JSONException ex) {
 // edited, to include @Arthur's comment
 // e.g. in case JSONArray is valid as well...
 try {
 new JSONArray(test);
 } catch (JSONException ex1) {
 return false;
 }
 }
 return true;
}
</code></pre>
This code uses <a href="https://www.json.org/" rel="nofollow noreferrer">org.json</a> JSON API implementation that is available <a href="https://github.com/stleary/JSON-java" rel="nofollow noreferrer">on github</a>, <a href="http://mvnrepository.com/artifact/org.json/json" rel="nofollow noreferrer">in maven</a> and partially <a href="https://developer.android.com/reference/org/json/package-summary.html" rel="nofollow noreferrer">on Android</a>.

blocks|key|594432|text|对于Google+Gson，您可以使用JsonParser：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|594433|import+com.google.gson.JsonParser;

JsonParser+parser+=+new+JsonParser();
parser.parse(json_string);+//+throws+JsonSyntaxException|code-block|syntax|javascript|594434|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/google/gson^0|2|B|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]]]]

With <a href="https://github.com/google/gson">Google Gson</a> you can use JsonParser:

<pre><code>import com.google.gson.JsonParser;

JsonParser parser = new JsonParser();
parser.parse(json_string); // throws JsonSyntaxException
</code></pre>

blocks|key|594227|text|您可以使用JSONUtils库中提供的.mayBeJSON(String+str)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|594228|entityMap|0|LINK|mutability|MUTABLE|url|http://json-lib.sourceforge.net/apidocs/jdk15/net/sf/json/util/JSONUtils.html|1|http://json-lib.sourceforge.net/apidocs/jdk15/net/sf/json/util/JSONUtils.html#mayBeJSON%2528java.lang.String%2529^0|5|9|0|J|M|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

You could use the <a href="http://json-lib.sourceforge.net/apidocs/jdk15/net/sf/json/util/JSONUtils.html#mayBeJSON%28java.lang.String%29" rel="noreferrer">.mayBeJSON(String str)</a> available in the <a href="http://json-lib.sourceforge.net/apidocs/jdk15/net/sf/json/util/JSONUtils.html" rel="noreferrer">JSONUtils</a> library.

blocks|key|378511|text|下面是一个使用gson库进行严格json解析的工作示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|378512|public+static+JsonElement+parseStrict(String+json)+{
++++//+throws+on+almost+any+non-valid+json
++++return+new+Gson().getAdapter(JsonElement.class).fromJson(json);+
}|code-block|syntax|javascript|378513|有关更多信息和带有各种无效示例的扩展测试用例，请参阅我在How+to+check+if+JSON+is+valid+in+Java+using+GSON中的其他详细答案。|378514|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/google/gson|1|https://stackoverflow.com/questions/43233898/how-to-check-if-json-is-valid-in-java-using-gson/47890960#47890960^0|7|4|0|0|0|S|1C|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@$A|10|B|11|1|12]]|C|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]]]

Here is a working example for strict json parsing with <a href="https://github.com/google/gson" rel="nofollow noreferrer">gson</a> library:

<pre><code>public static JsonElement parseStrict(String json) {
 // throws on almost any non-valid json
 return new Gson().getAdapter(JsonElement.class).fromJson(json); 
}
</code></pre>

See also my other detailed answer in <a href="https://stackoverflow.com/questions/43233898/how-to-check-if-json-is-valid-in-java-using-gson/47890960#47890960">How to check if JSON is valid in Java using GSON</a> with more info and extended test case with various non-valid examples.

blocks|key|594569|text|使用javax.json库的解决方案：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|594570|import+javax.json.*;

public+boolean+isTextJson(String+text)+{
++++try+{
++++++++Json.createReader(new+StringReader(text)).readObject();
++++}+catch+(JsonException+ex)+{
++++++++try+{
++++++++++++Json.createReader(new+StringReader(text)).readArray();
++++++++}+catch+(JsonException+ex2)+{
++++++++++++return+false;
++++++++}
++++}
++++return+true;
}|code-block|syntax|javascript|594571|entityMap^0|2|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|$]]

A solution using the <code>javax.json</code> library:

<pre><code>import javax.json.*;

public boolean isTextJson(String text) {
 try {
 Json.createReader(new StringReader(text)).readObject();
 } catch (JsonException ex) {
 try {
 Json.createReader(new StringReader(text)).readArray();
 } catch (JsonException ex2) {
 return false;
 }
 }
 return true;
}
</code></pre>

blocks|key|378362|text|在这里，您可以找到一个可以验证JSON文件的tool，或者您可以使用任何JSON库对您的JSON文件进行反序列化，如果操作成功，那么它应该是有效的(例如google-json，如果它解析的输入不是有效的JSON，它将抛出一个异常)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|378363|entityMap|0|LINK|mutability|MUTABLE|url|http://jsontools.berlios.de/|1|http://google-gson.googlecode.com/svn/trunk/gson/docs/javadocs/index.html^0|M|4|0|24|B|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

Here you can find a <a href="http://jsontools.berlios.de/" rel="nofollow">tool</a> that can validate a JSON file, or you could just deserialize your JSON file with any JSON library and if the operation is successful then it should be valid (<a href="http://google-gson.googlecode.com/svn/trunk/gson/docs/javadocs/index.html" rel="nofollow">google-json</a> for example that will throw an exception if the input it is parsing is not valid JSON).

blocks|key|594481|text|使用Playframework+2.6，java+api中的Json库也可以用来简单地解析字符串。字符串可以是json数组的json元素。因为返回值在这里并不重要，所以我们只需要捕获解析错误来确定字符串是否是正确的json字符串。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|594482|++++import+play.libs.Json;

++++public+static+Boolean+isValidJson(String+value)+{
++++++++try{
++++++++++++Json.parse(value);
++++++++++++return+true;
++++++++}+catch(final+Exception+e){
++++++++++++return+false;
++++++++}
++++}|code-block|syntax|javascript|594483|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Using Playframework 2.6, the Json library found in the java api can also be used to simply parse the string. The string can either be a json element of json array. Since the returned value is not of importance here we just catch the parse error to determine that the string is a correct json string or not.

<pre><code> import play.libs.Json;

 public static Boolean isValidJson(String value) {
 try{
 Json.parse(value);
 return true;
 } catch(final Exception e){
 return false;
 }
 }
</code></pre>

blocks|key|378703|text|正如您所看到的，有很多解决方案，它们主要是解析JSON来检查它，最后您必须解析它才能确定。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|378704|但是，根据上下文的不同，您可以通过预检查来提高性能。|378705|当我调用API时，我所做的就是检查第一个字符是'{‘，最后一个字符是'}’。如果不是这样，我就不创建解析器了。|378706|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

As you can see, there is a lot of solutions, they mainly parse the JSON to check it and at the end you will have to parse it to be sure.

But, depending on the context, you may improve the performances with a pre-check.

What I do when I call APIs, is just checking that the first character is '{' and the last is '}'. If it's not the case, I don't bother creating a parser.

blocks|key|594403|text|我已经找到了一个非常简单的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|594404|请先安装此库的net.sf.json-lib。|offset|length|style|CODE|594405|++++import+net.sf.json.JSONException;

++++import+net.sf.json.JSONSerializer;

++++private+static+boolean+isValidJson(String+jsonStr)+{
++++++++boolean+isValid+=+false;
++++++++try+{
++++++++++++JSONSerializer.toJSON(jsonStr);
++++++++++++isValid+=+true;
++++++++}+catch+(JSONException+je)+{
++++++++++++isValid+=+false;
++++++++}
++++++++return+isValid;
++++}

++++public+static+void+testJson()+{
++++++++String+vjson+=+"{\"employees\":+[{+\"firstName\":\"John\"+,+\"lastName\":\"Doe\"+},{+\"firstName\":\"Anna\"+,+\"lastName\":\"Smith\"+},{+\"firstName\":\"Peter\"+,+\"lastName\":\"Jones\"+}]}";
++++++++String+ivjson+=+"{\"employees\":+[{+\"firstName\":\"John\"+,,+\"lastName\":\"Doe\"+},{+\"firstName\":\"Anna\"+,+\"lastName\":\"Smith\"+},{+\"firstName\":\"Peter\"+,+\"lastName\":\"Jones\"+}]}";
++++++++System.out.println(""%2BisValidJson(vjson));+//+true
++++++++System.out.println(""%2BisValidJson(ivjson));+//+false
++++}|code-block|syntax|javascript|594406|好了。尽情享受|594407|entityMap^0|0|7|F|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@$D|S|E|T|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|U|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

I have found a very simple solution for it. 

Please first install this library <code>net.sf.json-lib</code> for it.

<pre><code> import net.sf.json.JSONException;

 import net.sf.json.JSONSerializer;

 private static boolean isValidJson(String jsonStr) {
 boolean isValid = false;
 try {
 JSONSerializer.toJSON(jsonStr);
 isValid = true;
 } catch (JSONException je) {
 isValid = false;
 }
 return isValid;
 }

 public static void testJson() {
 String vjson = "{\"employees\": [{ \"firstName\":\"John\" , \"lastName\":\"Doe\" },{ \"firstName\":\"Anna\" , \"lastName\":\"Smith\" },{ \"firstName\":\"Peter\" , \"lastName\":\"Jones\" }]}";
 String ivjson = "{\"employees\": [{ \"firstName\":\"John\" ,, \"lastName\":\"Doe\" },{ \"firstName\":\"Anna\" , \"lastName\":\"Smith\" },{ \"firstName\":\"Peter\" , \"lastName\":\"Jones\" }]}";
 System.out.println(""+isValidJson(vjson)); // true
 System.out.println(""+isValidJson(ivjson)); // false
 }
</code></pre>

Done. Enjoy

blocks|key|594509|text|import+static+net.minidev.json.JSONValue.isValidJson;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|594510|然后调用此函数，传入JSON字符串:)|unstyled|594511|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>import static net.minidev.json.JSONValue.isValidJson;
</code></pre>

and then call this function passing in your JSON String :)

blocks|key|378738|text|你可以试试下面的代码，对我很管用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|378739|+import+org.json.JSONObject;
+import+org.json.JSONTokener;

+public+static+JSONObject+parseJsonObject(String+substring)
+{
++return+new+JSONObject(new+JSONTokener(substring));
+}|code-block|syntax|javascript|378740|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can try below code, worked for me:
<pre><code> import org.json.JSONObject;
 import org.json.JSONTokener;

 public static JSONObject parseJsonObject(String substring)
 {
 return new JSONObject(new JSONTokener(substring));
 }
</code></pre>

blocks|key|378630|text|您可以使用Validol声明性验证库中的WellFormedJson类。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|378631|声明本身可能如下所示：|378632|new+WellFormedJson(
++++new+Unnamed<>(Either.right(new+Present<>(jsonRequestString)))
)|code-block|syntax|javascript|378633|检查阶段如下所示：|378634|++++Result<JsonElement>+result+=
++++++++(new+WellFormedJson(
++++++++++++new+Named<>(
++++++++++++++++"vasya",
++++++++++++++++Either.right(
++++++++++++++++++++new+Present<>(
++++++++++++++++++++++++"{\"guest\":{\"name\":\"Vadim+Samokhin\",\"email\":\"samokhinvadim@gmail.com\"},\"source\":1,\"items\":[{\"id\":1900},{\"id\":777}]}"
++++++++++++++++++++)
++++++++++++++++)
++++++++++++)
++++++++))
++++++++++++.result();

++++assertTrue(result.isSuccessful());
++++assertEquals(
++++++++"{\"guest\":{\"name\":\"Vadim+Samokhin\",\"email\":\"samokhinvadim@gmail.com\"},\"source\":1,\"items\":[{\"id\":1900},{\"id\":777}]}",
++++++++result.value().raw().toString()
++++);
++++assertEquals(
++++++++"{\"name\":\"Vadim+Samokhin\",\"email\":\"samokhinvadim@gmail.com\"}",
++++++++result.value().raw().getAsJsonObject().get("guest").toString()
++++);|378635|对于这样一个简单的任务，它看起来有点过头了，但是当您必须验证一个复杂的请求时，它就会大放异彩。查看validol的quick+start+section。|378636|entityMap|0|LINK|mutability|MUTABLE|url|http://validol.readthedocs.io/|1|https://validol.readthedocs.io/en/latest/quick_start.html^0|K|E|5|7|0|0|0|0|0|0|1L|J|1|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]]|E|$]]|$1|F|3|G|5|6|7|18|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|19|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1A|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1B|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1C|8|@]|D|@$9|1D|A|1E|1|1F]]|E|$]]|$1|S|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]|10|$5|V|W|X|E|$Y|11]]]]

You can use <code>WellFormedJson</code> class from <a href="http://validol.readthedocs.io" rel="nofollow noreferrer">Validol</a> declarative validation library.

The declaration itself could look like the following:

<pre><code>new WellFormedJson(
 new Unnamed&lt;&gt;(Either.right(new Present&lt;&gt;(jsonRequestString)))
)
</code></pre>

The check phase looks like that:

<pre><code> Result&lt;JsonElement&gt; result =
 (new WellFormedJson(
 new Named&lt;&gt;(
 "vasya",
 Either.right(
 new Present&lt;&gt;(
 "{\"guest\":{\"name\":\"Vadim Samokhin\",\"email\":\"samokhinvadim@gmail.com\"},\"source\":1,\"items\":[{\"id\":1900},{\"id\":777}]}"
 )
 )
 )
 ))
 .result();

 assertTrue(result.isSuccessful());
 assertEquals(
 "{\"guest\":{\"name\":\"Vadim Samokhin\",\"email\":\"samokhinvadim@gmail.com\"},\"source\":1,\"items\":[{\"id\":1900},{\"id\":777}]}",
 result.value().raw().toString()
 );
 assertEquals(
 "{\"name\":\"Vadim Samokhin\",\"email\":\"samokhinvadim@gmail.com\"}",
 result.value().raw().getAsJsonObject().get("guest").toString()
 );
</code></pre>

It might seem like an overkill for such a simple task, but it shines when you have to validate a complex request. Check out validol's <a href="https://validol.readthedocs.io/en/latest/quick_start.html" rel="nofollow noreferrer">quick start section</a>.

How do I validate a JSON string in Java? Or could I parse it using regular expressions?

How to check whether a given string is valid JSON in Java

如何在Java中验证JSON字符串？或者我可以使用正则表达式来解析它？

问如何在Java中检查给定字符串是否为有效的JSON
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