Springboot使用RestTemplate发送Post请求postForEntity (application-json)的坑

Springboot使用RestTemplate发送Post请求postForEntity (application-json)的坑| Id | Title | DateAdded | SourceUrl | PostType | Body | BlogId | Description | DateUpdated | IsMarkdown | EntryName | CreatedTime | IsActive | AutoDesc | AccessPermission |

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| 16334421| Springboot使用RestTemplate发送Post请求postForEntity (application/json)的坑| 2022-06-01T15:32:00| | BlogPost|

当使用RestTemplate进行http请求时，的确很方便，但是当需要进行post请求时遇到了坑

1POST传递参数：采用 LinkedMultiValueMap ，不能使用HashMap

String url = 'http://posturl';
  MultiValueMap<String, String> map= new LinkedMultiValueMap<String, String>();        
 map.add("shopid","1");       
 HttpHeaders headers = new HttpHeaders();       
 headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);        
HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<MultiValueMap<String, String>>(map, headers);        
return restTemplate.postForEntity(url, request,String.class);

注意上面的请求支持参数类型均为String类型，如果MultiValueMap<String, Object> LinkedMultiValueMap 会将value放进list中，key --> [value]

2 采用JSONObject或者实体类传递参数

        RestTemplate restTemplate = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
        headers.setContentType(type);
        headers.add("Accept", MediaType.APPLICATION_JSON.toString());
    JSONObject param </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> JSONObject();
    param.put(</span>"username", "123"<span style="color: #000000;">);
    
    HttpEntity</span>&lt;String&gt; formEntity = <span style="color: #0000ff;">new</span> HttpEntity&lt;String&gt;<span style="color: #000000;">(param, headers);

    String result </span>= restTemplate.postForObject(url, formEntity, String.<span style="color: #0000ff;">class</span>);</pre>

public class LinkedMultiValueMap<K, V> implements MultiValueMap<K, V>, Serializable, Cloneable {
    private static final long serialVersionUID = 3801124242820219131L;
    private final Map<K, List<V>> targetMap;
</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> LinkedMultiValueMap() {
    </span><span style="color: #0000ff;">this</span>.targetMap = <span style="color: #0000ff;">new</span><span style="color: #000000;"> LinkedHashMap();
}

</span><span style="color: #0000ff;">public</span> LinkedMultiValueMap(<span style="color: #0000ff;">int</span><span style="color: #000000;"> initialCapacity) {
    </span><span style="color: #0000ff;">this</span>.targetMap = <span style="color: #0000ff;">new</span><span style="color: #000000;"> LinkedHashMap(initialCapacity);
}

</span><span style="color: #0000ff;">public</span> LinkedMultiValueMap(Map&lt;K, List&lt;V&gt;&gt;<span style="color: #000000;"> otherMap) {
    </span><span style="color: #0000ff;">this</span>.targetMap = <span style="color: #0000ff;">new</span><span style="color: #000000;"> LinkedHashMap(otherMap);
}

@Nullable
</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> V getFirst(K key) {
    List</span>&lt;V&gt; values = (List)<span style="color: #0000ff;">this</span><span style="color: #000000;">.targetMap.get(key);
    </span><span style="color: #0000ff;">return</span> values != <span style="color: #0000ff;">null</span> &amp;&amp; !values.isEmpty() ? values.get(0) : <span style="color: #0000ff;">null</span><span style="color: #000000;">;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> add(K key, @Nullable V value) {
    List</span>&lt;V&gt; values = (List)<span style="color: #0000ff;">this</span>.targetMap.computeIfAbsent(key, (k) -&gt;<span style="color: #000000;"> {
        </span><span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span><span style="color: #000000;"> LinkedList();
    });
    values.add(value);
}
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> addAll(K key, List&lt;? <span style="color: #0000ff;">extends</span> V&gt;<span style="color: #000000;"> values) {
    List</span>&lt;V&gt; currentValues = (List)<span style="color: #0000ff;">this</span>.targetMap.computeIfAbsent(key, (k) -&gt;<span style="color: #000000;"> {
        </span><span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span><span style="color: #000000;"> LinkedList();
    });
    currentValues.addAll(values);
}
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> addAll(MultiValueMap&lt;K, V&gt;<span style="color: #000000;"> values) {
    Iterator var2 </span>=<span style="color: #000000;"> values.entrySet().iterator();
    </span><span style="color: #0000ff;">while</span><span style="color: #000000;">(var2.hasNext()) {
        Entry</span>&lt;K, List&lt;V&gt;&gt; entry =<span style="color: #000000;"> (Entry)var2.next();
        </span><span style="color: #0000ff;">this</span><span style="color: #000000;">.addAll(entry.getKey(), (List)entry.getValue());
    }
}
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> set(K key, @Nullable V value) {
    List</span>&lt;V&gt; values = <span style="color: #0000ff;">new</span><span style="color: #000000;"> LinkedList();
    values.add(value);
    </span><span style="color: #0000ff;">this</span><span style="color: #000000;">.targetMap.put(key, values);
}
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> setAll(Map&lt;K, V&gt;<span style="color: #000000;"> values) {
    values.forEach(</span><span style="color: #0000ff;">this</span><span style="color: #000000;">::set);
}
</span><span style="color: #0000ff;">public</span> Map&lt;K, V&gt;<span style="color: #000000;"> toSingleValueMap() {
    LinkedHashMap</span>&lt;K, V&gt; singleValueMap = <span style="color: #0000ff;">new</span> LinkedHashMap(<span style="color: #0000ff;">this</span><span style="color: #000000;">.targetMap.size());
    </span><span style="color: #0000ff;">this</span>.targetMap.forEach((key, values) -&gt;<span style="color: #000000;"> {
        </span><span style="color: #0000ff;">if</span> (values != <span style="color: #0000ff;">null</span> &amp;&amp; !<span style="color: #000000;">values.isEmpty()) {
            singleValueMap.put(key, values.get(</span>0<span style="color: #000000;">));
        }

    });
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> singleValueMap;
}</span></pre>