https://qiita.com/sotoiwa/items/15cac258ed90d7861bdf
https://qiita.com/rinaxsumomo/items/9d0776f8a3e506fdebc4

Libertyの性能情報を取得する記事を見て、やってみたら、ハマったことをメモ。

Jsoup で basic認識のやり方がわからない。
Jsoup で https にアクセスするとエラーになる。
Gson で配列の解析方法がわからない。

上記３つは、以下のソースで実現できる。
特に難しいことやってないので、説明は省く。

SSLHelper はこちらから：
https://stackoverflow.com/questions/40742380/how-to-resolve-jsoup-error-unable-to-find-valid-certification-path-to-requested

SSLHelper.java

package liberty;

import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.X509Certificate;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

import org.jsoup.Connection;
import org.jsoup.Jsoup;

public class SSLHelper {

    static public Connection getConnection(String url) {
        return Jsoup.connect(url).sslSocketFactory(SSLHelper.socketFactory());
    }

    static private SSLSocketFactory socketFactory() {
        TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() {
            public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                return new X509Certificate[0];
            }

            public void checkClientTrusted(X509Certificate[] certs, String authType) {
            }

            public void checkServerTrusted(X509Certificate[] certs, String authType) {
            }
        } };

        try {
            SSLContext sslContext = SSLContext.getInstance("SSL");
            sslContext.init(null, trustAllCerts, new java.security.SecureRandom());
            SSLSocketFactory result = sslContext.getSocketFactory();
            return result;
        } catch (NoSuchAlgorithmException | KeyManagementException e) {
            throw new RuntimeException("Failed to create a SSL socket factory", e);
        }
    }
}

LibertyJvmStats.java

package liberty;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Base64;
import java.util.List;

import org.jsoup.nodes.Document;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

public class LibertyJvmStats {

    public static void main(String[] args) throws IOException {
        String username = "jmxadmin";
        String password = "password";
        String login = username + ":" + password;
        String base64login = new String(Base64.getEncoder().encode(login.getBytes()));

        // https://localhost:9443/IBMJMXConnectorREST/mbeans/WebSphere%3atype%3dThreadPoolStats%2cname%3dDefault%20Executor/attributes
        // https://localhost:9443/IBMJMXConnectorREST/mbeans/WebSphere%3Aname%3Ddefault_host%2FIBMJMXConnectorREST%2Ctype%3DSessionStats/attributes
        Document document = SSLHelper.getConnection("https://localhost:9443/IBMJMXConnectorREST/mbeans/WebSphere%3Atype%3DJvmStats/attributes") //
                .header("Authorization", "Basic " + base64login) //
                .ignoreContentType(true) //
                .ignoreHttpErrors(false) //
                .get();
        Gson gson = new Gson();
        List<LibertyJvmStats_Bean> list = gson.fromJson(document.text(), TypeToken.getParameterized(ArrayList.class, LibertyJvmStats_Bean.class).getType());
        list.forEach(val -> {
            switch (val.name) {
            case "UpTime":
                long time = Long.parseLong(val.value.value) / 1000 / 60;
                System.out.println(String.format("%12s : %d min", val.name, time));
                break;
            case "Heap":
            case "FreeMemory":
            case "UsedMemory":
                long value = Long.parseLong(val.value.value) / 1024 / 1024;
                System.out.println(String.format("%12s : %d mb", val.name, value));
                break;
            default:
                System.out.println(String.format("%12s : %s", val.name, val.value.value));
            }
        });
    }

    private class LibertyJvmStats_Bean {
        public String name;
        public LibertyJvmStats_Bean_value value;

        public class LibertyJvmStats_Bean_value {
            public String value;
            public String type;
        }
    }
}

ちなみに、https://localhost:9443/IBMJMXConnectorREST/mbeans/WebSphere%3Atype%3DJvmStats/attributes
の戻り値はこちら：

[
	{
		"name": "ProcessCPU",
		"value": {
			"value": "0.0",
			"type": "java.lang.Double"
		}
	},
	{
		"name": "Heap",
		"value": {
			"value": "543162368",
			"type": "java.lang.Long"
		}
	},
	{
		"name": "FreeMemory",
		"value": {
			"value": "348815256",
			"type": "java.lang.Long"
		}
	},
	{
		"name": "GcTime",
		"value": {
			"value": "244",
			"type": "java.lang.Long"
		}
	},
	{
		"name": "UsedMemory",
		"value": {
			"value": "194347112",
			"type": "java.lang.Long"
		}
	},
	{
		"name": "GcCount",
		"value": {
			"value": "18",
			"type": "java.lang.Long"
		}
	},
	{
		"name": "UpTime",
		"value": {
			"value": "625122",
			"type": "java.lang.Long"
		}
	}
]