blocks|key|2390433|text|一种方法是将JSON转换为java.util.Map，修改映射，然后从那里开始(这可能意味着将映射序列化为JSON)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2390434|这种方法符合我的偏好，即在正确的工作中使用正确的API，最大限度地减少使用像Gson这样的工具来处理序列化/反序列化(这就是我所理解的设计它的目的)。也就是说，不使用Gson+API作为替代数据结构。|2390435|entityMap^0|D|D|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

One approach would be to just convert the JSON to a <code>java.util.Map</code>, modify the Map, and go from there (which may mean serializing the Map back to JSON).

This approach meets my preference to work with the right API for the right job, minimizing the use of tools like Gson to just handle serialization/deserialization (which is what I understand it was designed for). That is, to not use the Gson API as a replacement data structure.

blocks|key|2390467|text|GSON有两个单独的API(可以组合)：一个用于序列化和反序列化，另一个用于流。如果您想在没有内存开销或使用动态结构(而不是静态POJO)的情况下处理JSON流，您可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2390468|循环创建循环(在我的示例中，我使用StringWriter);|2390469|create+a+JsonReader;|unordered-list-item|2390470|
|2390471|make+a+JsonWriter，该循环使用来自阅读器的事件，并将它们提供给编写器，可能会进行更改、添加、省略等。|2390472|2390473|循环将由单个switch语句组成，该语句必须包含所有可能的事件(共10个)。即使是最简单的示例也必须包含所有这些内容，因此下面的代码看起来相当冗长。但它很容易扩展，进一步的扩展不会让它变得更长。|2390474|将"test"：1对附加到每个对象的示例如下所示：|2390475|public+class+Whatever+{

static+void+streamandmodify(JsonReader+reader,+JsonWriter+writer)+throws+IOException+{
++++while+(true)+{
++++++++JsonToken+token+=+reader.peek();
++++++++switch+(token)+{
++++++++//+most+cases+are+just+consume+the+event
++++++++//+and+pass+an+identical+one+to+the+writer
++++++++case+BEGIN_ARRAY:
++++++++++++reader.beginArray();
++++++++++++writer.beginArray();
++++++++++++break;
++++++++case+END_ARRAY:
++++++++++++reader.endArray();
++++++++++++writer.endArray();
++++++++++++break;
++++++++case+BEGIN_OBJECT:
++++++++++++reader.beginObject();
++++++++++++writer.beginObject();

++++++++++++//+this+is+where+the+change+happens:
++++++++++++writer.name("test");
++++++++++++writer.value(1);
++++++++++++break;
++++++++case+END_OBJECT:
++++++++++++reader.endObject();
++++++++++++writer.endObject();
++++++++++++break;
++++++++case+NAME:
++++++++++++String+name+=+reader.nextName();
++++++++++++writer.name(name);
++++++++++++break;
++++++++case+STRING:
++++++++++++String+s+=+reader.nextString();
++++++++++++writer.value(s);
++++++++++++break;
++++++++case+NUMBER:
++++++++++++String+n+=+reader.nextString();
++++++++++++writer.value(new+BigDecimal(n));
++++++++++++break;
++++++++case+BOOLEAN:
++++++++++++boolean+b+=+reader.nextBoolean();
++++++++++++writer.value(b);
++++++++++++break;
++++++++case+NULL:
++++++++++++reader.nextNull();
++++++++++++writer.nullValue();
++++++++++++break;
++++++++case+END_DOCUMENT:
++++++++++++return;
++++++++}
++++}
}


public+static+void+main(String[]+args)+throws+IOException+{
++++//+just+for+test:
++++JsonReader+jr+=+new+JsonReader(new+StringReader("{\"a\":1,+\"b\":{\"c\":[1,2,3,{},{}]}}"));
++++StringWriter+sw+=+new+StringWriter();
++++JsonWriter+jw+=+new+JsonWriter(sw);
++++streamandmodify(jr,+jw);
++++System.out.println(sw.getBuffer().toString());
}
}|code-block|syntax|javascript|2390476|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|Z|8|@]|9|@]|A|$]]|$1|I|3|J|5|F|7|10|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|12|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|13|8|@]|9|@]|A|$]]|$1|P|3|Q|5|R|7|14|8|@]|9|@]|A|$S|T]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

GSON has two separate APIs (that can be combined): one is used for serialization and deserialization, and the other for streaming. If you want to process streams of JSON without memory overhead or using dynamic structures (rather than static POJOs) you can do something like:

<ul>
<li>create a JsonWriter (in my example I use StringWriter);</li>
<li>create a JsonReader;</li>
<li>make a loop that consumes events from the reader and feeds them to the writer, possibly making changes, additions, omissions etc.</li>
</ul>

The loop will consist of a single switch statement that must have a case all the possible events (10 of them). Even the simplest example must have all of them, so the code below looks rather verbose. But it is very easy to extend and further extensions will not make it much longer.

An example that appends "test": 1 pair to each object looks something like:

<pre><code>public class Whatever {

static void streamandmodify(JsonReader reader, JsonWriter writer) throws IOException {
 while (true) {
 JsonToken token = reader.peek();
 switch (token) {
 // most cases are just consume the event
 // and pass an identical one to the writer
 case BEGIN_ARRAY:
 reader.beginArray();
 writer.beginArray();
 break;
 case END_ARRAY:
 reader.endArray();
 writer.endArray();
 break;
 case BEGIN_OBJECT:
 reader.beginObject();
 writer.beginObject();

 // this is where the change happens:
 writer.name("test");
 writer.value(1);
 break;
 case END_OBJECT:
 reader.endObject();
 writer.endObject();
 break;
 case NAME:
 String name = reader.nextName();
 writer.name(name);
 break;
 case STRING:
 String s = reader.nextString();
 writer.value(s);
 break;
 case NUMBER:
 String n = reader.nextString();
 writer.value(new BigDecimal(n));
 break;
 case BOOLEAN:
 boolean b = reader.nextBoolean();
 writer.value(b);
 break;
 case NULL:
 reader.nextNull();
 writer.nullValue();
 break;
 case END_DOCUMENT:
 return;
 }
 }
}


public static void main(String[] args) throws IOException {
 // just for test:
 JsonReader jr = new JsonReader(new StringReader("{\"a\":1, \"b\":{\"c\":[1,2,3,{},{}]}}"));
 StringWriter sw = new StringWriter();
 JsonWriter jw = new JsonWriter(sw);
 streamandmodify(jr, jw);
 System.out.println(sw.getBuffer().toString());
}
}
</code></pre>

blocks|key|5918689|text|jsonString是一个普通的Java字符串；因此，您可以使用Java语言的标准字符串函数对其进行任意修改，并将子串key1替换为Test1|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5918690|jsonString+=+"[{\"key1\":\"Test\",\"key2\":\"World\"},{\"key1\":\"Nice\",\"key2\":\"Town\"}]";|code-block|syntax|javascript|5918691|当然，字符串在Java语言中是不可变的，因此首先将其转换为StringBuilder可能会在内存使用方面提供更好的性能。|5918692|entityMap^0|1N|4|1U|5|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

The jsonString is a plain, ordinary Java String; so you can modify it whatever you like using the standards String functions of Java and replace the substring <code>key1</code> with <code>Test1</code>:

<pre><code>jsonString = "[{\"key1\":\"Test\",\"key2\":\"World\"},{\"key1\":\"Nice\",\"key2\":\"Town\"}]";
</code></pre>

Of course, String in Java are immutable so converting it first to a StringBuilder will possibly give you a better performance in term of memory usage.

blocks|key|4503191|text|您总是可以获得与JsonElement不同的类型，或者使用JsonElement.getAsJsonObject转换为对象(如果可能)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4503192|String+jsonString+=+"[{\"key1\":\"Hello\",\"key2\":\"World\"},+...]";

JsonArray+jsonArray+=+gson.fromJson(jsonString,+JsonElement.class).getAsJsonArray();
JsonObject+firstObject+=+jsonArray.get(i).getAsJsonObject();
firstObject.addProperty("key1",+"Test");|code-block|syntax|javascript|4503193|我之前错了；似乎没有JsonArray适配器；您必须获得一个JsonElement并使用强制转换工具。|4503194|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You can always get a different type than JsonElement, or use JsonElement.getAsJsonObject to cast to an Object (if possible).

<pre><code>String jsonString = "[{\"key1\":\"Hello\",\"key2\":\"World\"}, ...]";

JsonArray jsonArray = gson.fromJson(jsonString, JsonElement.class).getAsJsonArray();
JsonObject firstObject = jsonArray.get(i).getAsJsonObject();
firstObject.addProperty("key1", "Test");
</code></pre>

I was wrong earlier; there seems to be no JsonArray adapter; you'll have to get a JsonElement and use the casting tool.

blocks|key|5918745|text|这是我想出的最短的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5918746|JsonElement+je+=+new+Gson().fromJson(jsonString,+JsonElement.class);
JsonObject+jo+=+je.getAsJsonObject();
jo.add("key",+value);|code-block|syntax|javascript|5918747|有了JsonObject之后，gson有很多方法可以操作它。|5918748|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Here's the shortest I came up with.

<pre><code>JsonElement je = new Gson().fromJson(jsonString, JsonElement.class);
JsonObject jo = je.getAsJsonObject();
jo.add("key", value);
</code></pre>

Once you have the JsonObject, gson has many methods to manipulate it.

blocks|key|5918790|text|使用GSON+JsonArray+Java8修改json|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5918791|如何使用GSON修改JSON中的值的示例|5918792|import+com.google.gson.Gson;
import+com.google.gson.JsonArray;
import+com.google.gson.JsonElement;
import+com.google.gson.JsonObject;

public+class+ModifyJson+{
++++public+static+void+main(String[]+args)+{
++++++++String+data+=+"[{\"ct_pk\":24,\"ct_name\":\"SISTEMA+DE+PRUEBAS\"},"
++++++++++++++++%2B+"{\"ct_pk\":1,\"ct_name\":\"CAPITAL+FEDERAL\"},"+%2B
++++++++++++++++"{\"ct_pk\":5,\"ct_name\":\"SISTEMA+DE+PRUEBAS+DOS\"}]";

++++++++System.out.println("before................."+%2B+data);

++++++++JsonArray+jsonArray+=+new+Gson().fromJson(data,+JsonElement.class).getAsJsonArray();
++++++++JsonArray+jsonArray2+=+new+JsonArray();
++++++++for+(JsonElement+pa+:+jsonArray)+{
++++++++++++JsonObject+jsonObject2+=+pa.getAsJsonObject();
++++++++++++String+ct_name+=+jsonObject2.get("ct_name").getAsString();
++++++++++++if+(ct_name.equals("SISTEMA+DE+PRUEBAS"))+{
++++++++++++++++jsonObject2.addProperty("ct_name",+"TODOS");
++++++++++++}
++++++++++++jsonArray2.add(jsonObject2);
++++++++}
++++++++System.out.println("after.................."+%2BjsonArray2);
++++}
}|code-block|syntax|javascript|5918793|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|$]]

Modify json with GSON JsonArray Java 8

Example of how to use GSON to modify a value within a JSON

<pre><code>import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

public class ModifyJson {
 public static void main(String[] args) {
 String data = "[{\"ct_pk\":24,\"ct_name\":\"SISTEMA DE PRUEBAS\"},"
 + "{\"ct_pk\":1,\"ct_name\":\"CAPITAL FEDERAL\"}," +
 "{\"ct_pk\":5,\"ct_name\":\"SISTEMA DE PRUEBAS DOS\"}]";

 System.out.println("before................." + data);

 JsonArray jsonArray = new Gson().fromJson(data, JsonElement.class).getAsJsonArray();
 JsonArray jsonArray2 = new JsonArray();
 for (JsonElement pa : jsonArray) {
 JsonObject jsonObject2 = pa.getAsJsonObject();
 String ct_name = jsonObject2.get("ct_name").getAsString();
 if (ct_name.equals("SISTEMA DE PRUEBAS")) {
 jsonObject2.addProperty("ct_name", "TODOS");
 }
 jsonArray2.add(jsonObject2);
 }
 System.out.println("after.................." +jsonArray2);
 }
}
</code></pre>

I want to modify a json content without converting it into a POJO. I am using GSON Library.

Following are the use case:

<pre><code>String jsonString = "[{\"key1\":\"Hello\",\"key2\":\"World\"},{\"key1\":\"Nice\",\"key2\":\"Town\"}]";

JsonElement jsonElement = gson.fromJson(jsonString, JsonElement.class); 
</code></pre>

Is there any way where I can set value of key1 to some value (let say "Test") in each array, without converting things into POJO

Modify json with GSON without using a POJO

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想修改json内容而不将其转换为POJO。我正在使用GSON库。以下是使用案例：String jsonString = "[{\"key1\":\"Hello\",\"key2\":\"World\"},{\"key1\":\"Nice\",\"key2\":\"Town\"}]";JsonElement jsonE...

问使用GSON修改json而不使用POJO。
EN

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问使用GSON修改json而不使用POJO。EN