How to configure RestTemplate in springboot

The content of this article is about the method of configuring RestTemplate in springboot. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Background: Recently, an intermediate system was built at work, using the RestTemplate framework to call the restful interface of the third system. The caller used polling to call the relevant interfaces of this system, during which heaps occurred many times. Memory overflow, system suspended animation, general Java's built-in Java memory analysis tool analyzed the dump file generated by the system and found that an object has not been recycled, occupying 98% of the heap memory. Use MAT to analyze the thread where the object is located, and found that it is related to the use of resttemplate Threads, and the heap objects generated by related threads are not cleared after resttemplate is closed. Searching relevant information online shows that traditional HttpClient is prone to heap memory overflow in high request volume and high concurrency situations, while using Apache This phenomenon rarely occurs in the HttpClient instance CloseableHttpClient, and RestTemplate uses org.springframework.http.client.ClientHttpRequest by default, which needs to be replaced in the configuration file;

This article mainly records the configuration of RestTemplate in springboot .

1. Add dependencies:

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.3</version>
</dependency>

2. Configure CloseableHttpClient related properties and set up regular cleanup connections

Package com.**.config;
import lombok.extern.slf4j.Slf4j;
import org.apache.http.HeaderElement;
import org.apache.http.HeaderElementIterator;
import org.apache.http.HttpResponse;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.connectionKeepAliveStrategy;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.comn.ssl.TrustSelfsignedStrategy;
import org.apache.http.Impl.client.CloseableHttpClient;
import org.apache.http.Impl.client.Httpclients;
import org.apache.http.Impl.conn.PoolingHttpclientConnectionManager;
import org.apache.http.Message.BasicHeaderELementIterator;
import org.apache.http.protocol.HTTP;
import org.apache.http.protocol.HttpContext;
import org.apache.http.ssl.SSLContextBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.Scheduled;
import java.security.KeyManagementException;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.util.concurrent.TimeUnit;
/* *
 * Supports both HTTP and HTTPS
 * Uses a connect ion pool to re-use connect ions and save overhead of creat ing connect ions.
 * Has a custom connection keep-al ive strategy  (to apply a default keep-alive if one isn't specified)
 * starts an idle connection monitor to cont inuously clean up stale connections.
 */
@Slf4j
@Configuration
public class HttpClientConfig {

    //Determines the timeout in milliseconds until a  connection is established.
    private static final int CONNECT_TIMEOUT = 30000;

    //The  timeout when requesting a connection from the connection manager.
    private static final int REQUEST_ TIMEOUT = 30000;

    //The timeout for waiting for data
    private static final int SOCKET_ TIMEOUT = 60000;

    private static final int MAX_ TOTAL CONNECTIONS = 50;
    private static final int DEFAULT KEEP ALIVE_ TIME_ MIlLIS = 20 * 1000;
    private static final int CLOSE_ IDLE_ CONNECTION WAIT_ TIME_ SECS = 30;

    @Bean
    public PoolingHttpClientConnectionManager poolingConnectionManager() {

        SSLContextBuilder builder = new SSLContextBuilder ();
        try {
            builder.loadTrustMaterial(null, new TrustSelfSignedStrategy());
        }catch (NoSuchAlgorithmException | KeyStoreException e) {
            log.error ("Pooling Connection Manager Initialisation failure because of"+ e.getMessage(), e);
        }
        SSLConnectionSocketFactory sslsf = null;
        try{
            sslsf = new SSLConnectionSocketFactory (builder.build());
        } catch (KeyManagementException | NoSuchAlgorithmException e) {
            log.error("Pooling Connection Manager Initialisation failure because of" + e.GetMessage(), e);
        }
        Registry <ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder
                .create ().register ("https", sslsf)
                .register (id: "http", new PlainConnectionSocketFactory ())
                .build ();

        PoolingHttpclientConnectionManager poolingConnectionManager = new PoolingHttpclientConnectionManager  (socketFactoryRegistry);
        poolingConnectionManager.setMaxTotal(MAX_ TOTAL CONNECTIONS);
        return poolingConnectionManager;
    }

    @Bean
    public ConnectionKeepAliveStrategy connectionKeepAliveStrategy () {
        return new ConnectionKeepAliveStrategy (){
            @override
            public long getKeepAliveDuration (HttpResponse response, HttpContext context) {
                HeaderElementIterator it = new BasicHeaderElementIterator
                        (response.headerIterator(HTTP.CONN_KEEP_ALIVE));
                while (it.hasNext()) {
                    HeaderElement he = it.nextElement();
                    String param = he.getName();
                    String value = he.getValue();
                    if (value != null && param.equalsIgnoreCase("timeout")) {
                        return Long.parseLong(value) * 1000;
                    }
                }
                return DEFAULT_ KEEP_ALIVE_TIME_MILlIS;
            }
        };
    }
    @Bean
    public CloseableHttpClient httpClient () {
        RequestConfig requestConfig = RequestConfig.custom ()
                .setConnectionRequestTimeout(REQUEST_TIMEOUT)
                .setConnectTimeout (CONNECT_TIMEOUT)
                .setSocketTimeout (SOCKET_TIMEOUT).build();

        return Httpclients.custom ()
                .setDefaultRequestConfig(requestConfig)
                .setConnectionManager (poolingConnectionManager ())
                .setKeepAliveStrategy (connectionKeepAliveStrategy ())
                .build ();
    }

    @Bean
    public Runnable idleConnectionMonitor (final PoolingHttpClientConnectionManager connectionManager){
        return new Runnable() {
            @override
            @Scheduled(fixedDelay = 10000)
            public void run() {
                try {
                    if (connectionManager != null) {
                        log.trace("run IdleConnectionMonitor - Closing expired and idle connections... ");
                        connectionManager.closeExpiredConnections();
                        connectionManager.closeIdleConnections(CLOSE_IDLE_CONNECTION_WAIT_TIME_SECS, TimeUnit.SECONDS);
                    } else
                        log.info("run IdleConnectionMonitor - Http Client Connection manager is not initialised");
                } catch (Exception e) {
                    log.error("run IdleConnectionMonitor - Exception occurred.msg={}. ", e.getMessage());
                }
            }
        };
    }
}

3. Replace the default httpClient in TestTemplate

Package com.**.config;

import lombok.extern.slf4j.Slf4j;
import org.apache.http.impl.client.CloseableHttpClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.Httpcomponentsclienthttprequestfactory;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.scheduling.TaskScheduler;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
import org.springframework.web.client.RestTemplate;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.List;


@Slf4j
@Configuration
public class RestTemplateConfig {

    @Autowired
    CloseableHttpClient httpClient;

    @Bean
    public RestTemplate restTemplate () {

        RestTemplate restTemplate = new RestTemplate(clientHttpRequestFactory());

        /**
         * StringHttpMessogeConverter 默认使用 IS0-8859-编码，此处修改为 UTF-8
         */
        List<HttpMessageConverter<?>> messageConverters = restTemplate.getMessageConverters();
        Iterator<HttpMessageConverter<?>> iterator = messageConverters.iterator();
        while (iterator.hasNext()) {
            HttpMessageConverter<?> converter = iterator.next();
            if (converter instanceof StringHttpMessageConverter) {
                ((StringHttpMessageConverter) converter).setDefaultCharset(Charset.forName("UTF-8"));
            }
        }
        return restTemplate;
    }

    @Bean
    public HttpComponentsClientHttpRequestFactory clientHttpRequestfactory () {
        HttpComponentsClientHttpRequestFactory clientHttpRequestFactory =  new HttpComponentsClientHttpRequestfactory();
        clientJttpRequestFactory.setHttpClient(httpClient);
        return clientHttpRequestFactory;
    }

    @Bean
    public TaskScheduler taskScheduler() {
        ThreadPooolTaskScheduler scheduler = new ThreadPooolTaskScheduler();
        scheduler.setThreadNamePrefix("poolScheduler");
        scheduler.setPoolSize (50);
        return scheduler;
    }
}

4. Inject the RestTemplate class into the startup class:

@Bean
public RestTemplate restTemplate(RestTemplateBuilder builder){
       return builder.build();
}

At this point, RestTemplate can be used normally.

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