使用Spring的RestTemplate时，默认的超时值是无限的。

默认情况下，RestTemplate使用SimpleClientHttpRequestFactory，然后使用HttpURLConnection。

默认情况下为HttpURLConnection的超时时间为0 - 即无限的，除非它已经被设置这些属性：

-Dsun.net.client.defaultConnectTimeout=TimeoutInMiliSec 
-Dsun.net.client.defaultReadTimeout=TimeoutInMiliSec 

SimpleClientHttpRequestFactory 源码。

public class SimpleClientHttpRequestFactory implements ClientHttpRequestFactory, AsyncClientHttpRequestFactory {
    private static final int DEFAULT_CHUNK_SIZE = 4096;
    private Proxy proxy;
    private boolean bufferRequestBody = true;
    private int chunkSize = 4096;
    private int connectTimeout = -1;
    private int readTimeout = -1;
    private boolean outputStreaming = true;
    private AsyncListenableTaskExecutor taskExecutor;
    //...
    public void setConnectTimeout(int connectTimeout) {
        this.connectTimeout = connectTimeout;
    }
    //...
    public void setReadTimeout(int readTimeout) {
        this.readTimeout = readTimeout;
    }
}

其 setConnectTimeout 和 setReadTimeout 方法，且默认值为 -1。

设置超时时间：

        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
        factory.setConnectTimeout(60000);
        factory.setReadTimeout(300000);
        this.restTemplate = new RestTemplate(factory);