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1. Mapped Statements collection does not contain value for后面是什么类什么方法之类的：

错误原因有几种： 1)、mapper.xml中没有加入namespace 2)、mapper.xml中的方法和接口mapper的方法不对应 3)、mapper.xml没有加入到mybatis-config.xml中(即总的配置文件)，例外：配置了mapper文件的包路径的除外 4)、mapper.xml文件名和所写的mapper名称不相同。 org.apache.ibatis.binding.BindingException: Invalid bound statement (not found) 查看读取mapper.xml配置，例如是否是读取的 /*Mapper.xml,然后新写的xml名字是否包含后缀xxMapper.xml

2. Linux安装jdk

1).下载jdk-8u65-linux-x64.tar.gz版;
2).将文件jdk-8u65-linux-x64.gz移动到/usr/java/下，并解压：
tar -xzvf  jdk-8u65-linux-x64.gz
3).在/etc/profile文件中，配置环境变量，是JDK在所有用户中生效：打开/etc/profile文件　　vi /etc/profile
4).编辑profile文件，在最后添加：
export JAVA_HOME=/usr/java/jdk1.8.0_65
export JRE_HOME=$JAVA_HOME/jre
export CLASSPATH=.:$JAVA_HOME/lib:$JRE_HOME/lib
export PATH=$JAVA_HOME/bin:$PATH
保存退出后，执行source /etc/profile使修改的环境变量生效
5).使用java -version命令测试是否成功

Mybatis - Invalid bound statement (not found)

Check if scanned the config of mapperLocations

Maven打包时将外部引入的jar包 打包到项目jar包中

<includeSystemScope>true</includeSystemScope>

Java connect Linux to get server info:

ganymed-ssh2-262.jar

<dependency>
  <groupId>ch.ethz.ganymed</groupId>
  <artifactId>ganymed-ssh2</artifactId>
  <version>262</version>
</dependency>

Connection connection = new Connection(hostname);
connection.connect();
boolean isAuthenticated = connection.authenticateWithPassword(username, password);
if (!isAuthenticated) {
	throw new IOException("Authentication failed.");
}
Session session = connection.openSession();
session.execCommand(command);
BufferedReader reader = new BufferedReader(new InputStreamReader(session.getStdout()));
String line;
while ((line = reader.readLine()) != null) {
	System.out.println(line);
}
session.close();
connection.close();

start a jar`

nohup java -jar starfish.jar > nohup.out 2>&1  -Duser.timezone=Asia/Shanghai &

convert timestamp to date

// 1727666666286
long timestamp = System.currentTimeMillis();
// Mon Sep 30 03:16:40 GMT+08:00 2024
Date date = new Date(timestamp);

mybatis collection属性值就是传入的List或array对象在自己封装的map里面的key

<foreach item="id" collection="ids" open="and id in (" separator="," close=")">
	#{id}
</foreach>

SSL 连接 MQTT 的代码示例

import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

import javax.net.ssl.*;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.*;
import java.security.cert.CertificateException;

public class MqttSslConnectionExample {
    private static final String BROKER_URL = "ssl://your-mqtt-broker-url:8883";
    private static final String CLIENT_ID = "JavaMqttClient";
    private static final String TOPIC = "test/topic";
    private static final String MESSAGE = "Hello, MQTT over SSL!";
    private static final String KEY_STORE_FILE = "path/to/your/keystore.jks";
    private static final String KEY_STORE_PASSWORD = "your-keystore-password";
    private static final String TRUST_STORE_FILE = "path/to/your/truststore.jks";
    private static final String TRUST_STORE_PASSWORD = "your-truststore-password";

    public static void main(String[] args) {
        try {
            // 创建 SSLContext
            SSLContext sslContext = createSSLContext();

            // 创建 MQTT 客户端选项
            MqttConnectOptions connOpts = new MqttConnectOptions();
            connOpts.setSocketFactory(sslContext.getSocketFactory());
            connOpts.setCleanSession(true);

            // 创建 MQTT 客户端
            MqttClient sampleClient = new MqttClient(BROKER_URL, CLIENT_ID, new MemoryPersistence());

            // 设置回调
            sampleClient.setCallback(new MqttCallback() {
                @Override
                public void connectionLost(Throwable cause) {
                    System.out.println("Connection lost: " + cause.getMessage());
                }

                @Override
                public void messageArrived(String topic, MqttMessage message) throws Exception {
                    System.out.println("Received message on topic " + topic + ": " + new String(message.getPayload()));
                }

                @Override
                public void deliveryComplete(IMqttDeliveryToken token) {
                    System.out.println("Message delivered");
                }
            });

            // 连接到 MQTT 代理
            sampleClient.connect(connOpts);
            System.out.println("Connected to MQTT broker via SSL");

            // 订阅主题
            sampleClient.subscribe(TOPIC);
            System.out.println("Subscribed to topic: " + TOPIC);

            // 发布消息
            MqttMessage mqttMessage = new MqttMessage(MESSAGE.getBytes());
            sampleClient.publish(TOPIC, mqttMessage);
            System.out.println("Published message: " + MESSAGE + " to topic: " + TOPIC);

            // 断开连接
            sampleClient.disconnect();
            System.out.println("Disconnected from MQTT broker");
        } catch (MqttException | KeyManagementException | NoSuchAlgorithmException | KeyStoreException | CertificateException | IOException e) {
            e.printStackTrace();
        }
    }

    private static SSLContext createSSLContext() throws NoSuchAlgorithmException, KeyStoreException, IOException, CertificateException, KeyManagementException {
        // 加载密钥库
        KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
        keyStore.load(new FileInputStream(KEY_STORE_FILE), KEY_STORE_PASSWORD.toCharArray());

        // 加载信任库
        KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
        trustStore.load(new FileInputStream(TRUST_STORE_FILE), TRUST_STORE_PASSWORD.toCharArray());

        // 创建 KeyManagerFactory
        KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
        kmf.init(keyStore, KEY_STORE_PASSWORD.toCharArray());

        // 创建 TrustManagerFactory
        TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
        tmf.init(trustStore);

        // 创建 SSLContext
        SSLContext sslContext = SSLContext.getInstance("TLS");
        sslContext.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);

        return sslContext;
    }
}