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    Connecting to Database

    Last updated: 2024-02-02 15:17:07
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      By default, only CVM instances in the same VPC subnet can access a CDWPG cluster. If you need to access it over the public network, apply for a public IP.
      After creating a cluster, you need to use the database client to connect to the database before you can use the database services. Connect to the database with the client tool psql as instructed below.
      1. Get the cluster access address: Connect to the database through the IP and port number in the JDBC URL of the cluster.
      2. Connect to the cluster database: Install the client and connect to the cluster database.

      Prerequisites

      1. You have obtained the password of the database admin account for the CDWPG cluster. The password is the one set when the cluster is created.
      2. You have obtained the IP, port number, VPC, and subnet information to access the created CDWPG cluster.

      Getting Cluster Access Address and Local Network Information

      Select the corresponding cluster with the details as shown below. Get the information of the vpc-aejsd98p VPC and subnet-83knqldq subnet. The IP to access CDWPG is 10.0.6.10, the port number is 5432, and the login account is lambuser.
      

      Connecting to Cluster Database on Command Line

      Select a CVM instance in the obtained vpc-aejsd98p VPC and subnet-83knqldq subnet or purchase one if there is none. Log in to the instance and run the following command to install the PostgreSQL client.
      yum install -y postgresql.x86_64
      Run the following SQL command and enter the password set during cluster creation to log in.
      psql –h10.0.6.10  –p5432  –dpostgres  –Ulambuser

      Connecting to Database with JDBC

      Get the JDBC officially provided by PostgresSQL here.
      Or, add the following configuration to the pom.xml file:
      <dependencies>
              <dependency>
                  <groupId>org.postgresql</groupId>
                  <artifactId>postgresql</artifactId>
                  <version>42.2.2</version>
              </dependency>
      </dependencies>

      Sample code

      package com.qcloud.snova_conn;
      
      import java.io.InputStream;
      import java.sql.Connection;
      import java.sql.DriverManager;
      import java.sql.PreparedStatement;
      import java.sql.ResultSet;
      import java.sql.ResultSetMetaData;
      import java.sql.Statement;
      import java.sql.Timestamp;
      import java.util.ArrayList;
      import java.util.List;
      import java.util.Properties;
      import java.sql.Connection;  
      import java.sql.ResultSet;  
      import java.sql.SQLException;  
      import com.yammer.metrics.core.Meter;
      
      public class SnovaConn {
          /*
           * args: vip vport user pwd
           */
          public static void main(String[] args) throws ClassNotFoundException, SQLException {
      
              if (args.length < 4){
                       System.out.println("args err");
                       return;
              }
      
              String vip =  args[0];
              String vport =  args[1];
              String userName =  args[2];
              String userPwd =  args[3];
      
              System.out.printf("vip:%s, vport:%s, userName:%s, userPwd:%s\\n",vip, vport, userName, userPwd);
              String jdbcUrl = "jdbc:postgresql://" + vip+":"+vport+"/maxluo";
              System.out.printf("jdbcUrl:%s \\n",jdbcUrl);
      
              Class.forName("org.postgresql.Driver");  
              Connection snova = DriverManager.getConnection(jdbcUrl,userName,userPwd);  
              Statement st = snova.createStatement();  
              ResultSet rs = st.executeQuery("select * from test;");  
              while (rs.next()) {  
                      System.out.print(rs.getString(1));  
                      System.out.print("\\n");  
              }  
              rs.close();  
              st.close(); 
          }
      }

      pom.xml configuration

      <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
      <modelVersion>4.0.0</modelVersion>
      
      <groupId>com.qcloud</groupId>
      <artifactId>snova-conn</artifactId>
      <version>0.0.1-SNAPSHOT</version>
      <packaging>jar</packaging>
      
      <name>snova-conn</name>
      <url>http://maven.apache.org</url>
      
      <properties>
          <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
          <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
          <maven.compiler.source>1.8</maven.compiler.source>
          <maven.compiler.target>1.8</maven.compiler.target>
      </properties>
      
      <dependencies>
          <dependency>
              <groupId>mysql</groupId>
              <artifactId>mysql-connector-java</artifactId>
              <version>5.1.40</version>
          </dependency>
          <dependency>
              <groupId>org.postgresql</groupId>
              <artifactId>postgresql</artifactId>
              <version>42.2.2</version>
          </dependency>
          <dependency>
              <groupId>com.microsoft.sqlserver</groupId>
              <artifactId>mssql-jdbc</artifactId>
              <version>6.4.0.jre8</version>
          </dependency>
          <dependency>
              <groupId>com.yammer.metrics</groupId>
              <artifactId>metrics-core</artifactId>
              <version>2.2.0</version>
          </dependency>
          <dependency>
              <groupId>ch.qos.logback</groupId>
              <artifactId>logback-classic</artifactId>
              <version>1.1.9</version>
          </dependency>
      </dependencies>
      
      <build>
          <plugins>
              <plugin>
                  <artifactId>maven-assembly-plugin</artifactId>
                      <configuration>
                      <descriptorRefs>
                      <descriptorRef>jar-with-dependencies</descriptorRef>
                      </descriptorRefs>
                      </configuration>
                  <executions>
                      <execution>
                      <id>make-assembly</id>
                      <phase>package</phase>
                      <goals>
                      <goal>single</goal>
                      </goals>
                      </execution>
                  </executions>
              </plugin>
              <plugin>
                  <groupId>org.apache.maven.plugins</groupId>
                  <artifactId>maven-jar-plugin</artifactId>
                  <configuration>
                      <excludes>
                          <exclude>*.properties</exclude>
                          <exclude>*.xml</exclude>
                          <exclude>*.json</exclude>
                          <exclude>*.sh</exclude>
                      </excludes>
                  </configuration>
              </plugin>
              <plugin>
                  <groupId>org.apache.maven.plugins</groupId>
                  <artifactId>maven-dependency-plugin</artifactId>
                  <executions>
                      <execution>
                          <id>copy-dependencies</id>
                          <phase>package</phase>
                          <goals>
                              <goal>copy-dependencies</goal>
                          </goals>
                          <configuration>
                              <type>jar</type>
                              <includeTypes>jar</includeTypes>
                              <outputDirectory>
                                  ${project.build.directory}/lib
                              </outputDirectory>
                          </configuration>
                      </execution>
                  </executions>
              </plugin>
          </plugins>
      </build>
      </project>
      Then, use Maven to package the jar file and upload the jar package to the CVM instance (any instance in the VPC subnet where the CDWPG cluster resides).
      Run the following command to install JDK. 
      yum install java
      Run the following command:
      java –cp  snova-conn-0.0.1-SNAPSHOT-jar-with-dependencies.jar  com.qcloud.snova_conn.SnovaConn  10.0.8.5  5436   lambuser  lambpwd11
      Note:
      The VIP and port number are the address to access the CDWPG cluster, and the username and password are those entered during cluster creation as detailed above.
      Create a database and data table on the command line and insert a certain amount of data.
      The query result is as shown below, where you can read the data in the test table in the maxluo database created previously.
      
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