blocks|key|310362|text|更新2020年9月虽然我在这里的原始答案，多年前，似乎是有帮助的，并仍然得到越来越多的支持，我现在使用来自谷歌的GSON库，我发现它更直观。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|310363|我得到了以下代码：|310364|public+void+testJackson()+throws+IOException+{++
++++ObjectMapper+mapper+=+new+ObjectMapper();+
++++File+from+=+new+File("albumnList.txt");+
++++TypeReference<HashMap<String,Object>>+typeRef+
++++++++++++=+new+TypeReference<HashMap<String,Object>>()+{};

++++HashMap<String,Object>+o+=+mapper.readValue(from,+typeRef);+
++++System.out.println("Got+"+%2B+o);+
}+++|code-block|syntax|javascript|310365|它是从文件中读取的，但mapper.readValue()也会接受InputStream，您可以使用以下命令从字符串中获取InputStream：|offset|length|style|CODE|310366|new+ByteArrayInputStream(astring.getBytes("UTF-8"));+|310367|在my+blog上有更多关于映射器的解释。|310368|entityMap|0|LINK|mutability|MUTABLE|url|http://djna.wordpress.com/2010/03/12/json-strings-no-rest-using-the-jackson-parser/^0|0|0|0|B|I|X|B|1P|B|0|0|1|7|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|13|8|@$K|14|L|15|M|N]|$K|16|L|17|M|N]|$K|18|L|19|M|N]]|9|@]|A|$]]|$1|O|3|P|5|F|7|1A|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@$K|1C|L|1D|1|1E]]|A|$]]|$1|S|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

[Update Sept 2020] Although my original answer here, from many years ago, seems to be helpful and is still getting upvotes, I now use the GSON library from Google, which I find to be more intuitive.
I've got the following code:
<pre><code>public void testJackson() throws IOException { 
 ObjectMapper mapper = new ObjectMapper(); 
 File from = new File(&quot;albumnList.txt&quot;); 
 TypeReference&lt;HashMap&lt;String,Object&gt;&gt; typeRef 
 = new TypeReference&lt;HashMap&lt;String,Object&gt;&gt;() {};

 HashMap&lt;String,Object&gt; o = mapper.readValue(from, typeRef); 
 System.out.println(&quot;Got &quot; + o); 
} 
</code></pre>
It's reading from a file, but <code>mapper.readValue()</code> will also accept an <code>InputStream</code> and you can obtain an <code>InputStream</code> from a string by using the following:
<pre><code>new ByteArrayInputStream(astring.getBytes(&quot;UTF-8&quot;)); 
</code></pre>
There's a bit more explanation about the mapper on <a href="http://djna.wordpress.com/2010/03/12/json-strings-no-rest-using-the-jackson-parser/" rel="noreferrer">my blog</a>.

blocks|key|310370|text|你得到的警告是由编译器完成的，而不是由库(或实用方法)完成的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|310371|直接使用Jackson的最简单方法是：|310372|HashMap<String,Object>+props;

//+src+is+a+File,+InputStream,+String+or+such
props+=+new+ObjectMapper().readValue(src,+new+TypeReference<HashMap<String,Object>>()+{});
//+or:
props+=+(HashMap<String,Object>)+new+ObjectMapper().readValue(src,+HashMap.class);
//+or+even+just:
@SuppressWarnings("unchecked")+//+suppresses+typed/untype+mismatch+warnings,+which+is+harmless
props+=+new+ObjectMapper().readValue(src,+HashMap.class);|code-block|syntax|javascript|310373|你调用的实用方法可能会做类似这样的事情。|310374|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Warning you get is done by compiler, not by library (or utility method).

Simplest way using Jackson directly would be:

<pre><code>HashMap&lt;String,Object&gt; props;

// src is a File, InputStream, String or such
props = new ObjectMapper().readValue(src, new TypeReference&lt;HashMap&lt;String,Object&gt;&gt;() {});
// or:
props = (HashMap&lt;String,Object&gt;) new ObjectMapper().readValue(src, HashMap.class);
// or even just:
@SuppressWarnings("unchecked") // suppresses typed/untype mismatch warnings, which is harmless
props = new ObjectMapper().readValue(src, HashMap.class);
</code></pre>

Utility method you call probably just does something similar to this.

blocks|key|3053917|text|试试TypeFactory。以下是Jackson+JSON+(2.8.4)的代码。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3053918|Map<String,+String>+result;
ObjectMapper+mapper;
TypeFactory+factory;
MapType+type;

factory+=+TypeFactory.defaultInstance();
type++++=+factory.constructMapType(HashMap.class,+String.class,+String.class);
mapper++=+new+ObjectMapper();
result++=+mapper.readValue(data,+type);|code-block|syntax|javascript|3053919|以下是Jackson+JSON的旧版本的代码。|3053920|Map<String,+String>+result+=+new+ObjectMapper().readValue(
++++data,+TypeFactory.mapType(HashMap.class,+String.class,+String.class));|3053921|entityMap^0|2|B|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

Try <code>TypeFactory</code>. Here's the code for Jackson JSON (2.8.4).

<pre><code>Map&lt;String, String&gt; result;
ObjectMapper mapper;
TypeFactory factory;
MapType type;

factory = TypeFactory.defaultInstance();
type = factory.constructMapType(HashMap.class, String.class, String.class);
mapper = new ObjectMapper();
result = mapper.readValue(data, type);
</code></pre>

Here's the code for an older version of Jackson JSON.

<pre><code>Map&lt;String, String&gt; result = new ObjectMapper().readValue(
 data, TypeFactory.mapType(HashMap.class, String.class, String.class));
</code></pre>

blocks|key|313289|text|从字符串转换为JSON映射：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|313290|Map<String,String>+map+=+new+HashMap<String,String>();

ObjectMapper+mapper+=+new+ObjectMapper();

map+=+mapper.readValue(string,+HashMap.class);|code-block|syntax|javascript|313291|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|$]]

Converting from String to JSON Map:

<pre><code>Map&lt;String,String&gt; map = new HashMap&lt;String,String&gt;();

ObjectMapper mapper = new ObjectMapper();

map = mapper.readValue(string, HashMap.class);
</code></pre>

blocks|key|310389|text|ObjectReader+reader+=+new+ObjectMapper().readerFor(Map.class);

Map<String,+String>+map+=+reader.readValue("{\"foo\":\"val\"}");|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|310390|请注意，reader实例是线程安全的。|unstyled|offset|length|style|CODE|310391|entityMap^0|0|4|6|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>ObjectReader reader = new ObjectMapper().readerFor(Map.class);

Map&lt;String, String&gt; map = reader.readValue("{\"foo\":\"val\"}");
</code></pre>

Note that <code>reader</code> instance is Thread Safe.

blocks|key|3267563|text|JavaType+javaType+=+objectMapper.getTypeFactory().constructParameterizedType(Map.class,+Key.class,+Value.class);
Map<Key,+Value>+map=objectMapper.readValue(jsonStr,+javaType);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3267564|我想这会解决你的问题。|unstyled|3267565|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>JavaType javaType = objectMapper.getTypeFactory().constructParameterizedType(Map.class, Key.class, Value.class);
Map&lt;Key, Value&gt; map=objectMapper.readValue(jsonStr, javaType);
</code></pre>

i think this will solve your problem.

blocks|key|312442|text|下面的方法对我很有效：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|312443|Map<String,+String>+propertyMap+=+getJsonAsMap(json);|code-block|syntax|javascript|312444|其中getJsonAsMap的定义如下：|offset|length|style|CODE|312445|public+HashMap<String,+String>+getJsonAsMap(String+json)
{
++++try
++++{
++++++++ObjectMapper+mapper+=+new+ObjectMapper();
++++++++TypeReference<Map<String,String>>+typeRef+=+new+TypeReference<Map<String,String>>()+{};
++++++++HashMap<String,+String>+result+=+mapper.readValue(json,+typeRef);

++++++++return+result;
++++}
++++catch+(Exception+e)
++++{
++++++++throw+new+RuntimeException("Couldnt+parse+json:"+%2B+json,+e);
++++}
}|312446|请注意，如果您的json中有子对象(因为它们不是String，它们是另一个HashMap)，这将失败，但如果您的json是属性的键值列表，则可以工作，如下所示：|312447|{
++++"client_id":+"my+super+id",
++++"exp":+1481918304,
++++"iat":+"1450382274",
++++"url":+"http://www.example.com"
}|312448|entityMap^0|0|0|2|C|0|0|O|6|11|7|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@$I|11|J|12|K|L]|$I|13|J|14|K|L]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|T|$]]

The following works for me:

<pre><code>Map&lt;String, String&gt; propertyMap = getJsonAsMap(json);
</code></pre>

where <code>getJsonAsMap</code> is defined like so:

<pre><code>public HashMap&lt;String, String&gt; getJsonAsMap(String json)
{
 try
 {
 ObjectMapper mapper = new ObjectMapper();
 TypeReference&lt;Map&lt;String,String&gt;&gt; typeRef = new TypeReference&lt;Map&lt;String,String&gt;&gt;() {};
 HashMap&lt;String, String&gt; result = mapper.readValue(json, typeRef);

 return result;
 }
 catch (Exception e)
 {
 throw new RuntimeException("Couldnt parse json:" + json, e);
 }
}
</code></pre>

Note that this will fail if you have child objects in your json (because they're not a <code>String</code>, they're another <code>HashMap</code>), but will work if your json is a key value list of properties like so:

<pre><code>{
 "client_id": "my super id",
 "exp": 1481918304,
 "iat": "1450382274",
 "url": "http://www.example.com"
}
</code></pre>

blocks|key|3054035|text|使用Google的Gson|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3054036|为什么不使用here中提到的谷歌的Gson|offset|length|3054037|非常直截了当地为我做了这件事：|3054038|HashMap<String,String>+map+=+new+Gson().fromJson(+yourJsonString,+new+TypeToken<HashMap<String,+String>>(){}.getType());|code-block|syntax|javascript|3054039|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/22033974/5320562^0|0|6|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@$D|W|E|X|1|Y]]|A|$]]|$1|F|3|G|5|6|7|Z|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

<h2>Using Google's Gson</h2>

Why not use Google's Gson as mentioned in <a href="https://stackoverflow.com/a/22033974/5320562">here</a>?

Very straight forward and did the job for me:

<pre><code>HashMap&lt;String,String&gt; map = new Gson().fromJson( yourJsonString, new TypeToken&lt;HashMap&lt;String, String&gt;&gt;(){}.getType());
</code></pre>

blocks|key|315471|text|下面是这个问题的通用解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|315472|public+static+<K+extends+Object,+V+extends+Object>+Map<K,+V>+getJsonAsMap(String+json,+K+key,+V+value)+{
++++try+{
++++++ObjectMapper+mapper+=+new+ObjectMapper();
++++++TypeReference<Map<K,+V>>+typeRef+=+new+TypeReference<Map<K,+V>>()+{
++++++};
++++++return+mapper.readValue(json,+typeRef);
++++}+catch+(Exception+e)+{
++++++throw+new+RuntimeException("Couldnt+parse+json:"+%2B+json,+e);
++++}
++}|code-block|syntax|javascript|315473|希望有一天有人会考虑创建一个util方法来转换为Map的任何键/值类型，因此回答如下:)|315474|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 is the generic solution to this problem.

<pre><code>public static &lt;K extends Object, V extends Object&gt; Map&lt;K, V&gt; getJsonAsMap(String json, K key, V value) {
 try {
 ObjectMapper mapper = new ObjectMapper();
 TypeReference&lt;Map&lt;K, V&gt;&gt; typeRef = new TypeReference&lt;Map&lt;K, V&gt;&gt;() {
 };
 return mapper.readValue(json, typeRef);
 } catch (Exception e) {
 throw new RuntimeException("Couldnt parse json:" + json, e);
 }
 }
</code></pre>

Hope someday somebody would think to create a util method to convert to any Key/value type of Map hence this answer :)

blocks|key|3054093|text|只是想给Kotlin一个答案|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3054094|val+propertyMap+=+objectMapper.readValue<Map<String,String>>(properties,+object+:+TypeReference<Map<String,+String>>()+{})|code-block|syntax|javascript|3054095|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|$]]

just wanted to give a Kotlin answer

<pre><code>val propertyMap = objectMapper.readValue&lt;Map&lt;String,String&gt;&gt;(properties, object : TypeReference&lt;Map&lt;String, String&gt;&gt;() {})
</code></pre>

I'm trying to do something like this but it doesn't work:

<pre><code>Map&lt;String, String&gt; propertyMap = new HashMap&lt;String, String&gt;();

propertyMap = JacksonUtils.fromJSON(properties, Map.class);
</code></pre>

But the IDE says: 

<blockquote>
 Unchecked assignment <code>Map to Map&lt;String,String&gt;</code>
</blockquote>

What's the right way to do this?
I'm only using Jackson because that's what is already available in the project, is there a native Java way of converting to/from JSON?

In PHP I would simply <code>json_decode($str)</code> and I'd get back an array. I need basically the same thing here.

How to convert a JSON string to a Map<String, String> with Jackson JSON

编译器

Kotlin

JSON

Java

我试着做这样的事情，但它不起作用：Map<String, String> propertyMap = new HashMap<String, String>();propertyMap = JacksonUtils.fromJSON(properties, Map.class);但是IDE说：未选中的 assignme...

问如何使用Jackson JSON将JSON字符串转换为Map<String、String>
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