1. 扩展 RestTemplate Get 方法， make GET with Request Body.

private static final class HttpComponentsClientHttpRequestWithBodyFactory extends HttpComponentsClientHttpRequestFactory
private static final class HttpGetRequestWithEntity extends HttpEntityEnclosingRequestBase

refer1： https://cleanprogrammer.net/making-get-request-with-body-using-spring-resttemplate/
refer2: https://mekaso.rocks/get-requests-with-a-request-body-spring-resttemplate-vs-apache-httpclient

2. RestTemplate 代理（proxy）设置

final String proxyUrl = "adc-opc-proxy.usdc1.oraclecloud.com";
//final String proxyUrl = "www-proxy-hqdc.us.oracle.com";
final int port = 80;

CredentialsProvider credsProvider = new BasicCredentialsProvider();
credsProvider.setCredentials(
        new AuthScope(proxyUrl, port),
        new UsernamePasswordCredentials("", ""));

HttpHost myProxy = new HttpHost(proxyUrl, port);
HttpClientBuilder clientBuilder = HttpClientBuilder.create();
clientBuilder.setProxy(myProxy).setDefaultCredentialsProvider(credsProvider).disableCookieManagement();
HttpClient httpClient = clientBuilder.build();

requestFactory.setHttpClient(httpClient);
RestTemplate.setRequestFactory(requestFactory);

3. RestTemplate OAuth

private String accessTokenUri = Configuration.getValue("accessTokenUri", "");
private String clientID = Configuration.getValue("clientID", "");
private String clientSecret = Configuration.getValue("clientSecret", "");
//private String scope = Configuration.getValue("scope", "");
//private String scope = Constants.esBaseUrl;
private String scope = Constants.scope;

public OAuth2ProtectedResourceDetails oscs() {
    ClientCredentialsResourceDetails details = new ClientCredentialsResourceDetails();
    details.setId("oscs");
    details.setClientId(clientID);
    details.setClientSecret(clientSecret);
    details.setAccessTokenUri(accessTokenUri);
    details.setTokenName("access_token");
    details.setScope(Arrays.asList(scope));
    return details;
}

public OAuth2RestTemplate oscsRestTemplate() {

    OAuth2RestTemplate template = new OAuth2RestTemplate(oscs());
    AccessTokenProvider accessTokenProvider = new AccessTokenProviderChain(
                Arrays.<AccessTokenProvider>asList(new ClientCredentialsAccessTokenProvider()));
    template.setAccessTokenProvider(accessTokenProvider);

    template.setRequestFactory(requestFactory);
    return template;
    }

4. 完整Class example

package rest.api.util;

import java.net.URI;
import java.util.Arrays;

import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpEntityEnclosingRequestBase;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.HttpClientBuilder;
import org.springframework.http.HttpMethod;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.security.oauth2.client.OAuth2RestTemplate;
import org.springframework.security.oauth2.client.resource.OAuth2ProtectedResourceDetails;
import org.springframework.security.oauth2.client.token.AccessTokenProvider;
import org.springframework.security.oauth2.client.token.AccessTokenProviderChain;
import org.springframework.security.oauth2.client.token.grant.client.ClientCredentialsAccessTokenProvider;
import org.springframework.security.oauth2.client.token.grant.client.ClientCredentialsResourceDetails;
import org.springframework.security.oauth2.config.annotation.web.configuration.EnableOAuth2Client;
import org.springframework.web.client.RestTemplate;

@EnableOAuth2Client
public class ResourceConfiguration {
    private String accessTokenUri = Configuration.getValue("accessTokenUri", "");
    private String clientID = Configuration.getValue("clientID", "");
    private String clientSecret = Configuration.getValue("clientSecret", "");
    //private String scope = Configuration.getValue("scope", "");
    //private String scope = Constants.esBaseUrl;
    private String scope = Constants.scope;

    public OAuth2ProtectedResourceDetails oscs() {
        ClientCredentialsResourceDetails details = new ClientCredentialsResourceDetails();
        details.setId("oscs");
        details.setClientId(clientID);
        details.setClientSecret(clientSecret);
        details.setAccessTokenUri(accessTokenUri);
        details.setTokenName("access_token");
        details.setScope(Arrays.asList(scope));
        return details;
    }

    public OAuth2RestTemplate oscsRestTemplate() {

        OAuth2RestTemplate template = new OAuth2RestTemplate(oscs());
        AccessTokenProvider accessTokenProvider = new AccessTokenProviderChain(
                Arrays.<AccessTokenProvider>asList(new ClientCredentialsAccessTokenProvider()));
        template.setAccessTokenProvider(accessTokenProvider);

        template.setRequestFactory(setRequestFactory());
        return template;
    }


    public RestTemplate oscsRestTemplateNoAuth() {
        RestTemplate template = new RestTemplate();
        template.setRequestFactory(setRequestFactory());
        return template;
    }

    private HttpComponentsClientHttpRequestWithBodyFactory setRequestFactory() {

        HttpComponentsClientHttpRequestWithBodyFactory requestFactory = new HttpComponentsClientHttpRequestWithBodyFactory();
        if (Constants.CONFIG_FILE_NAME.contains("Prod")) {
            final String proxyUrl = "adc-opc-proxy.usdc1.oraclecloud.com";
            //final String proxyUrl = "www-proxy-hqdc.us.oracle.com";
            final int port = 80;

            CredentialsProvider credsProvider = new BasicCredentialsProvider();
            credsProvider.setCredentials(
                    new AuthScope(proxyUrl, port),
                    new UsernamePasswordCredentials("", ""));

            HttpHost myProxy = new HttpHost(proxyUrl, port);
            HttpClientBuilder clientBuilder = HttpClientBuilder.create();
            clientBuilder.setProxy(myProxy).setDefaultCredentialsProvider(credsProvider).disableCookieManagement();
            HttpClient httpClient = clientBuilder.build();

            requestFactory.setHttpClient(httpClient);
        }
        return requestFactory;
    }

    private static final class HttpComponentsClientHttpRequestWithBodyFactory extends HttpComponentsClientHttpRequestFactory {
        @Override
        protected HttpUriRequest createHttpUriRequest(HttpMethod httpMethod, URI uri) {
            if (httpMethod == HttpMethod.GET) {
                return new HttpGetRequestWithEntity(uri);
            }
            return super.createHttpUriRequest(httpMethod, uri);
        }
    }

    private static final class HttpGetRequestWithEntity extends HttpEntityEnclosingRequestBase {
        public HttpGetRequestWithEntity(final URI uri) {
            super.setURI(uri);
        }

        @Override
        public String getMethod() {
            return HttpMethod.GET.name();
        }

    }

}