我实际上是在 Neo4j 中使用社区插件，并尝试通过 java 发出 POST 请求来查询 Neo4j 服务器。
我总是收到 java.io.IOException: Server returned HTTP response code: 400 虽然对相同 url 的类似调用通过 javascript 工作，但业务逻辑建议通过 java 进行调用。
这是我的代码片段：
String baseURL="ip_of_server";
StringBuilder builder = new StringBuilder();
try {
URL url = new URL(baseURL);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setDoInput(true);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", "application/json");
OutputStream os=connection.getOutputStream();
OutputStreamWriter writer = new OutputStreamWriter(os,Charset.forName("UTF-8"));
System.out.println(url);
Map<String, Object> params = new HashMap<String, Object>();
params.put("query", "start x = node(3) return x");
HashMap<String,String> test3= new HashMap<String,String>();
params.put("params", test3);
ObjectMapper temp = new ObjectMapper();
String testString= temp.writeValueAsString(params);
writer.write(testString);
writer.close();
os.close();
String line = null;
BufferedReader reader = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
while ((line = reader.readLine()) != null) {
builder.append(line);
}
System.out.println("Response from server for request : " + url.toString() + " is " );
System.out.println(builder.toString());
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
有什么建议么？