Connect to OceanBase Database by using a Tomcat connection pool

This topic introduces how to build an application by using a Tomcat connection pool, OceanBase Connector/J, and OceanBase Database. It also covers the use of the application for fundamental database operations, including table creation, data insertion, data deletion, data updating, and data query.

Download the tomcat-mysql-client sample project

Connect to OceanBase Database by using a Tomcat connection pool (MySQL mode)

Prerequisites

• You have installed OceanBase Database.
• You have installed JDK 1.8 and Maven.
• You have installed IntelliJ IDEA.

Procedure

1. Import the tomcat-mysql-client project into IntelliJ IDEA.
2. Obtain the connection information of OceanBase Database.
3. Modify the database connection information in the tomcat-mysql-client project.
4. Set up the Tomcat runtime environment of the tomcat-mysql-client project.
5. Run the tomcat-mysql-client project.

Step 1: Import the tomcat-mysql-client project into IntelliJ IDEA

1. Start IntelliJ IDEA and choose File > Open....

   

2. In the Open File or Project window, select the project files and click OK to import the files.

3. IntelliJ IDEA automatically recognizes the files and displays the project's directory structure, file list, module list, dependency relationships, and other details in the Project window. The Project window is typically positioned on the left side of the IntelliJ IDEA interface and is generally open by default. If the Project window is closed, you can reopen it by choosing View > Tool Windows > Project in the menu bar or by using the shortcut Alt + 1.

   Note

   When you import a project using IntelliJ IDEA, it will automatically detect the pom.xml file in the project, download the required dependency libraries based on the described dependencies in the file, and add them to the project.

4. View the project.

   

Step 2: Obtain the connection information of OceanBase Database

1. Contact the deployment personnel or administrator of OceanBase Database to obtain the connection string.

   obclient -hxx.xx.xx.xx -P2883 -uroot@sys#cluster -p**** -A
   

2. Fill in the URL below based on the OceanBase Database connection string.

   Note

   The URL is required in the application.properties file.

   jdbc:oceanbase://host:port/schema_name?user=$user_name&password=$password&characterEncoding=UTF-8
   

   The parameters are described as follows:

   • host: the IP address for connecting to OceanBase Database. For connection through ODP, this parameter is the IP address of an ODP. For direct connection, this parameter is the IP address of an OBServer node.
   • port: the port for connecting to OceanBase Database. For connection through ODP, the default value is 2883, which can be customized when ODP is deployed. For direct connection, the default value is 2881, which can be customized when OceanBase Database is deployed.
   • schema_name: the name of the schema to be accessed.
   • user_name: the tenant account. For connection through ODP, the tenant account can be in the username@tenant name#cluster name or cluster name:tenant name:username format. For direct connection, the tenant account is in the username@tenant name format.
   • password: the password of the account.
   • characterEncoding: the character encoding format for the database URL. Default value: utf8.

For more information about URL parameters, see Database URL.

Step 3: Modify the database connection information in the tomcat-mysql-client project

Modify the database connection information in the application.properties file based on the OceanBase Database connection information obtained in Step 2: Obtain the connection information of OceanBase Database.

Here is an example:

• The name of the database driver is: com.oceanbase.jdbc.Driver.
• The IP address of the OBServer node is 10.10.10.1.
• The port is 2881.
• The name of the database to be accessed is TEST.
• The tenant account is root@xymysql. xymysql is a MySQL user tenant created in OceanBase Database, and root is the username of the xymysql tenant.
• The password is ******.

The sample code is as follows:

#Apache Commons DBCP2 Connection Pool
#Database Connection Pool Driver Class Name
db.app.pool.driverClassName=com.oceanbase.jdbc.Driver
#Database URL
db.app.pool.url=jdbc:oceanbase://10.10.10.1/TEST?characterEncoding=UTF-8
#Database username
db.app.pool.username=root@xymysqll
#Database password
db.app.pool.password=******
#Initial size of connection pool
db.app.pool.initialSize=3
#Maximum number of connections in the connection pool
db.app.pool.maxTotal=10
#Maximum number of idle connections in the connection pool
db.app.pool.maxIdle=20
#Minimum number of idle connections in the connection pool
db.app.pool.minIdle=5
#Maximum wait time for obtaining connections (in milliseconds)
db.app.pool.maxWaitMillis=5000
#Verify the connection's query statement
db.app.pool.validationQuery=select 1 from dual

Step 4: Set up the Tomcat runtime environment of the tomcat-mysql-client project

1. Download Apache Tomcat 8.5.95.

   Download the compressed file of Apache Tomcat 8.5.95 from the official website of Apache Tomcat and decompress it to the installation directory.

2. Configure Tomcat in IntelliJ IDEA.

   Open IntelliJ IDEA and choose File > Settings > Plugins. In the search box in the middle of the Settings window, search for Smart Tomcat, download it, and then choose Apply. The Tomcat Server tab will appear at the bottom of the Settings window. Go to the Tomcat Server tab, click + on the right side, select the decompressed Tomcat directory, and then click Apply and OK.

   

3. Create a Tomcat runtime configuration.

   In the top toolbar of IntelliJ IDEA, choose Run > Edit Configurations. In the Run/Debug Configurations window, click +, select Tomcat Server, specify a name for the server in the Name field, select Tomcat sever from the Configuration drop-down list box for the installed version, and modify the value of Context path to /. Specify 8080 for the value of SSL port. In the Before launch section, click + and select Launch Web Browser. Click Edit and set the URL to http://localhost:8080/hello/getData. Click Apply and then OK.

   

4. Start the Tomcat server.

   In the top toolbar of IntelliJ IDEA, choose the Tomcat runtime configuration that you created and click the green triangle to start the Tomcat server. You can view the startup logs of the Tomcat server in the Run window of IntelliJ IDEA.

Step 5: Run the tomcat-mysql-client project

1. Determine the running path.

   In the top toolbar of IDEA, select the Tomcat run configuration that you created earlier. Click the green triangle to start the Tomcat server. In the Chrome or IE browser, open the http://localhost:8080/hello/getData path to view the running result.

2. View the running result.

   In the console window of IDEA, view the log information and output results of the project.

   • The result after data is inserted.

     tomcat connection pool test0
     tomcat connection pool test1
     tomcat connection pool test2
     tomcat connection pool test3
     tomcat connection pool test4
     tomcat connection pool test5
     tomcat connection pool test6
     tomcat connection pool test7
     tomcat connection pool test8
     tomcat connection pool test9
     

   • The result after data is modified.

     -----After modification-----
     POOl connection pool test0
     POOl connection pool test1
     POOl connection pool test2
     POOl connection pool test3
     POOl connection pool test4
     POOl connection pool test5
     POOl connection pool test6
     POOl connection pool test7
     POOl connection pool test8
     POOl connection pool test9
     

   • The result returned to the web interface.

     

Project code introduction

Click tomcat-mysql-client to download the project code, which is a compressed file named tomcat-mysql-client.

After decompressing it, you will find a folder named tomcat-mysql-client. The directory structure is as follows:

│--pom.xml
│
├─.idea
│
├─src
│  ├─main
│  │  ├─java
│  │  │  └─com
│  │  │      └─oceanbase
│  │  │          └─testtomcat
│  │  │              ├─config
│  │  │              │   └─UserConfig.java
│  │  │              │
│  │  │              ├─controller
│  │  │              │   └─UserController.java
│  │  │              │
│  │  │              └─pojo
│  │  │                  └─User.java
│  │  │
│  │  ├─resources
│  │  │    └─application.properties
│  │  │    
│  │  └─webapp    
│  │      └─WEB-INF
│  │          └─web.xml
│  │             
│  │                
│  │
│  └─test
│      └─java
│         
│
└─target

Here is a breakdown of the files and directories:

• pom.xml: the configuration file of the Maven project, which contains the dependencies, plug-ins, and build details of the project.
• .idea: the directory for storing project-related configuration information used in the Integrated Development Environment (IDE).
• src: the directory for storing the source code in the project.
• main: the directory for storing the main source code and resource files.
• java: the directory for storing the Java source code.
• com: the root directory for storing the Java package.
• oceanbase: the root directory for storing the project.
• testtomcat: the directory for storing code of the JFinal framework.
• config: the directory for storing configuration files, including the application configuration class files.
• UserConfig.java: the user configuration class file.
• controller: the controller directory for storing the controller class file.
• UserController.java: the controller class file.
• pojo: the directory for storing JavaBean or entity classes.
• User.java: a file for storing user entity classes.
• resources: the directory for storing resource files, such as configuration files and SQL files.
• application.properties: the configuration file for storing database connection information.
• webapp: the directory for storing the static resources and configuration file of the web application.
• WEB-INF: the directory for storing the configuration file and other protected resource files of the web application.
• web.xml: the deployment descriptor file of the web application.
• test: the directory for storing the test code and resource files.
• target: the directory for storing compiled class files and .jar packages.

Code in the pom.xml file

The pom.xml configuration file is as follows:

1. Declaration statement.

   Declare this file to be an XML file that uses XML standard 1.0 and character encoding UTF-8.

   **The sample code is as follows: **

   <?xml version="1.0" encoding="UTF-8"?>
   

2. Configure the namespaces and the POM model version in the POM.

   1. Use xmlns to set the POM namespace to http://maven.apache.org/POM/4.0.0.
   2. Use xmlns:xsi to set the XML namespace to http://www.w3.org/2001/XMLSchema-instance.
   3. Use xsi:schemaLocation to set the POM's namespace to http://maven.apache.org/POM/4.0.0, and the URI of the corresponding XSD file to http://maven.apache.org/xsd/maven-4.0.0.xsd.
   4. Use the <modelVersion> element to set the POM model version used by the POM file to 4.0.0.

   **The sample code is as follows: **

   <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>
   </project>
   

3. Configure basic information.

   1. Set the project group ID to com.oceanbase by using <groupId>.
   2. Set the project dependency to tomcat-mysql-client by using <artifactId>.
   3. Set the project's version to 1.0-SNAPSHOT by using <version>.
   4. Set the packaging mode of the project to WAR file (Web application archive) by using <packaging>.

   **The sample code is as follows: **

    <groupId>com.oceanbase</groupId>
    <artifactId>tomcat-mysql-client</artifactId>
    <version>1.0-SNAPSHOT</version>
    <!-- Packaging method (default to jar) -->
    <packaging>war</packaging>
   

4. Configure the Maven version.

   The <maven.compiler.source> and <maven.compiler.target> parameters are set to Java 8, which specifies both the source code version and target code version of the compiler.

   **The sample code is as follows: **

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
   

5. Configure core dependencies.

   1. Specify the dependency group as com.jfinal, the dependency name as jfinal, and the dependency version as 5.0.6. With this dependency, you can use the features of the JFinal framework.

      The sample code is as follows:

      <dependency>
          <groupId>com.jfinal</groupId>
          <artifactId>jfinal</artifactId>
          <version>5.0.6</version>
      </dependency>
      

   2. Specify the dependency group as com.alibaba, the dependency name as druid, and the dependency version as 1.2.8. With this dependency, you can use the Druid library to manage and optimize the establishment and release of database connections.

      The sample code is as follows:

      <dependency>
          <groupId>com.alibaba</groupId>
          <artifactId>druid</artifactId>
          <version>1.2.8</version>
      </dependency>
      

   3. Specify the dependency group as org.apache.commons, the dependency name as commons-dbcp2, and the dependency version as 2.9.0. With this dependency, you can use the Apache Commons DBCP2 library to manage and optimize the establishment and release of database connections.

      The sample code is as follows:

      <dependency>
          <groupId>org.apache.commons</groupId>
          <artifactId>commons-dbcp2</artifactId>
          <version>2.9.0</version>
      </dependency>
      

   4. Specify the dependency group as mysql, the dependency name as mysql-connector-java, and the dependency version as 5.1.40. With this dependency, you can use the client features, such as connections, queries, and transactions, provided by OceanBase Database.

      **The sample code is as follows: **

      <dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <version>5.1.40</version>
      </dependency>
      

application.properties

The application.properties file configures the connection information for connecting to OceanBase Database. It includes the class name of the database driver, the connection URL, the username, the password, and the connection pool configurations. These configurations are used to obtain and manage database connections in applications for database operations.

• Set the db.app.pool.driverClassName parameter to com.mysql.jdbc.Driver to connect to OceanBase Database.

• Set the db.app.pool.url parameter to the URL for connecting to the database.

• Set the db.app.pool.username parameter to the username for connecting to the database.

• Set the db.app.pool.password parameter to the password for connecting to the database.

• Set the db.app.pool.initialSize parameter to the initial size of the connection pool, which is 3 in this example. This means that three database connections are created when the database connection pool is initialized.

• Set the db.app.pool.maxTotal parameter to the maximum size of the connection pool, which is 10 in this example. This means that the connection pool can create at most 10 database connections.

• Set the db.app.pool.maxIdle parameter to the maximum number of idle connections in the connection pool, which is 20 in this example.

• Set the db.app.pool.minIdle parameter to the minimum number of idle connections in the connection pool, which is 5 in this example.

• Set the db.app.pool.maxWaitMillis parameter to the connection timeout period, which is 5000ms in this example. When a database connection is being obtained, if no connection is available in the pool and the timeout period is reached, a timeout exception is thrown.

• Set the db.app.pool.validationQuery parameter to the SQL query statement for validating a database connection, which is select 1 in this example. This means that when a connection is obtained from the connection pool, the system executes this query statement to verify the validity of the connection.

  The sample code is as follows:

    #Apache Commons DBCP2 Connection Pool
    #Database Connection Pool Driver Class Name
    db.app.pool.driverClassName=com.mysql.jdbc.Driver
    #Database URL
    db.app.pool.url=jdbc:mysql:////host:port/schema_name?characterEncoding=UTF-8
    #Database username
    db.app.pool.username=user_name
    #Database password
    db.app.pool.password=******
    #Initial size of connection pool
    db.app.pool.initialSize=3
    #Maximum number of connections in the connection pool
    db.app.pool.maxTotal=10
    #Maximum number of idle connections in the connection pool
    db.app.pool.maxIdle=20
    #Minimum number of idle connections in the connection pool
    db.app.pool.minIdle=5
    #Maximum wait time for obtaining connections (in milliseconds)
    db.app.pool.maxWaitMillis=5000
    #Verify the connection's query statement
    db.app.pool.validationQuery=select 1 
  

Common configurations for the DBCP connection pool in Tomcat:

Code in web.xml

The web.xml file is used to configure filters for web applications.

The content of the web.xml configuration file is as follows:

1. The XML declaration statement.

   Declare this file to be an XML file that uses XML standard 1.0 and character encoding UTF-8.

   The sample code is as follows:

   <?xml version="1.0" encoding="UTF-8"?>
   

2. The configuration of XML namespaces and the XML model version.

   1. Use xmlns:xsi to set the XML namespace to http://www.w3.org/2001/XMLSchema-instance.
   2. Use xmlns to set the XML namespace to http://java.sun.com/xml/ns/javaee.
   3. Use xsi:schemaLocation to set the XML namespace to http://java.sun.com/xml/ns/javaee, and the URI of the corresponding XSD file to http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd.
   4. Use <id> and <version> to set the ID of the web application to WebApp_ID and the version number to 3.0.

   The sample code is as follows:

    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
             xmlns="http://java.sun.com/xml/ns/javaee" 
             xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 
             id="WebApp_ID" 
             version="3.0">
   

3. The configuration of a JFinal filter.

   Configure a filter named jfinal for the web application to use the JFinal framework. Set the class of the filter to com.jfinal.core.JFinalFilter. Use the initialization parameter configClass to set the location of the configuration class of the JFinal framework to com.oceanbase.testtomcat.config.UserConfig. The JFinal filter allows you to use the JFinal framework in the web application and to configure the behavior of the JFinal framework based on the specified configuration class.

   The sample code is as follows:

    <filter>
        <filter-name>jfinal</filter-name>
        <filter-class>com.jfinal.core.JFinalFilter</filter-class>
        <init-param>
            <param-name>configClass</param-name>
            <!-- your jfinal configuration location -->
            <param-value>com.oceanbase.testtomcat.config.UserConfig</param-value>
        </init-param>
    </filter>
   

4. The configuration of mappings for the JFinal filter.

   Apply the jfinal filter to all request paths, namely, to all requests in the application.

   The sample code is as follows:

    <filter-mapping>
        <filter-name>jfinal</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
   

Introduction to the UserConfig.java file

The UserConfig.java file is used to configure the routing, plug-ins, database connections, and other related information of an application.

The code in the UserConfig.java file mainly includes the following parts:

1. Reference other classes and APIs.

   Declare the current file to contain the following APIs and classes:

   • StatFilter class: used to statistics the performance of database access.
   • JdbcConstants class: used to define constant values of database types.
   • WallFilter class: used to prevent SQL injection attacks.
   • PropKit class: used to read configuration files.
   • ActiveRecordPlugin class: used to operate databases.
   • Db class: used to execute database operations.
   • MysqlDialect class: used to specify the dialect of the database.
   • DruidPlugin class: used to connect to databases.
   • Engine class: used to configure the template engine.
   • UserController class: used to process requests related to users.
   • User class: used to transmit and store user data.

   The sample code is as follows:

   import com.alibaba.druid.filter.stat.StatFilter;
   import com.alibaba.druid.util.JdbcConstants;
   import com.alibaba.druid.wall.WallFilter;
   import com.jfinal.config.*;
   import com.jfinal.kit.PropKit;
   import com.jfinal.plugin.activerecord.ActiveRecordPlugin;
   import com.jfinal.plugin.activerecord.Db;
   import com.jfinal.plugin.activerecord.dialect.MysqlDialect;
   import com.jfinal.plugin.druid.DruidPlugin;
   import com.jfinal.template.Engine;
   import com.oceanbase.testjfinal.controller.UserController;
   import com.oceanbase.testjfinal.pojo.User;
   

2. Define the UserConfig class.

   You can rewrite the methods of the JFinalConfig class to configure the constants, routing, plug-ins, and database connections.

   1. Define the configConstant method.

      Use this method to configure the constants of the JFinal framework and read the configurations from the configuration file by using PropKit.

      The sample code is as follows:

      @Override
      public void configConstant(Constants constants) {
          PropKit.use("application.properties");
      }
      

   2. Define the configRoute method.

      Use this method to configure the routing mappings. Use the routes.add method to map the "/hello" path to the default access page of the UserController class.

      The sample code is as follows:

      @Override
      public void configRoute(Routes routes) {
          routes.add("/hello", UserController.class, "/");
      }
      

   3. Define the configEngine method.

      Use this method to configure the template engine.

      The sample code is as follows:

      @Override
      public void configEngine(Engine engine) {
      }
      

   4. Define the configPlugin method.

      Use this method to configure plug-ins of the application. Call the init method to initialize the database connection and table structure, create the DruidPlugin and ActiveRecordPlugin plug-ins, and add them to the plugins array. Additionally, call the addMapping method of the activeRecordPlugin to add mappings between database tables and entity classes. In this way, the TEST_USER table is mapped to the User class.

      The sample code is as follows:

      @Override
      public void configPlugin(Plugins plugins) {
          init();
          DruidPlugin druidPlugin = createDruidPlugin();
          plugins.add(druidPlugin);
      
          ActiveRecordPlugin activeRecordPlugin = createActiveRecordPlugin(druidPlugin);
          activeRecordPlugin.addMapping("TOMCAT_TEST", User.class);
          plugins.add(activeRecordPlugin);
      }
      

   5. Define the createDruidPlugin method.

      Use this method to create a DruidPlugin plug-in and configure the relevant parameters, including the size of the connection pool, SQL firewall, and error handling for connections.

      • Use the get method of PropKit to obtain the database connection-related attribute values from the configuration file. The attribute values include the URL, username, password, and driver class. Then create a DruidPlugin object and initialize it with the obtained attribute values.

      • Use the addFilter method to add a StatFilter instance to the DruidPlugin for performance statistics of database access. Create a WallFilter instance, set the database type to OceanBase by using the setDbType method, and add the WallFilter instance to the DruidPlugin for SQL firewall filtering.

      • Use the setInitialSize method to set the initial size of the connection pool; the setMaxPoolPreparedStatementPerConnectionSize method to set the maximum number of preprocessed statements per connection in the pool; the setTimeBetweenConnectErrorMillis method to set the time interval between two connection errors; and the setValidationQuery method to set the validation query statement for connections. Finally, return the created DruidPlugin instance.

        The sample code is as follows:

        private DruidPlugin createDruidPlugin() {
            DruidPlugin druidPlugin = new DruidPlugin(
                PropKit.get("db.app.pool.url"),
                PropKit.get("db.app.pool.username"),
                PropKit.get("db.app.pool.password"),
                PropKit.get("db.app.pool.driverClassName")
            );
        
            druidPlugin.addFilter(new StatFilter());
            WallFilter wallFilter = new WallFilter();
            wallFilter.setDbType(JdbcConstants.OCEANBASE);
            druidPlugin.addFilter(wallFilter);
        
            druidPlugin.setInitialSize(PropKit.getInt("db.app.pool.initialSize"));
            druidPlugin.setMaxPoolPreparedStatementPerConnectionSize(PropKit.getInt("db.app.pool.maxTotal"));
            druidPlugin.setTimeBetweenConnectErrorMillis(PropKit.getInt("db.app.pool.maxWaitMillis"));
            druidPlugin.setValidationQuery("select 1");
        
            return druidPlugin;
        }
        

   6. Define the init method.

      Use this method to initialize the database connection and create a database table. Call the initDbConnection method to initialize the database connection and return an ActiveRecordPlugin instance. Then execute an SQL statement to query whether the TOMCAT_TEST table exists in the database. If the TOMCAT_TEST table exists, execute the SQL statement DROP TABLE TOMCAT_TEST to drop the table. Next, execute the CREATE TABLE statement to create a database table named TOMCAT_TEST. This table contains the ID and USERNAME fields. Finally, disconnect from the ActiveRecordPlugin plug-in and release the database connection.

      The sample code is as follows:

      public void init() {
          ActiveRecordPlugin arp = initDbConnection();
      
          // Check if table exists
          boolean tableExists = Db.queryInt("SELECT COUNT(*) FROM information_schema.TABLES WHERE TABLE_SCHEMA = 'TEST' AND TABLE_NAME = 'TOMCAT_TEST'") > 0;
      
          // Drop table if it exists
          if (tableExists) {
              Db.update("DROP TABLE TOMCAT_TEST");
          }
      
          // Create table
          String sql = "CREATE TABLE TOMCAT_TEST (ID int, USERNAME varchar(50))";
          Db.update(sql);
      
          arp.stop();
      }
      

   7. Define the initDbConnection method.

      Use this method to initialize the database connection. First, call the createDruidPlugin method to create a DruidPlugin object and assign it to the druidPlugin variable. This method is responsible for creating and configuring the DruidPlugin object for managing the database connection pool. Then call the createActiveRecordPlugin method to create an ActiveRecordPlugin object and pass the druidPlugin object as a parameter to the method. This method is responsible for creating and configuring the ActiveRecordPlugin object for managing database operations. Next, call the druidPlugin.start method to start the DruidPlugin and initialize the database connection pool. Finally, call the activeRecordPlugin.start method to start the ActiveRecordPlugin. This method will initialize the relevant database operation settings based on the configurations.

      The sample code is as follows:

      private ActiveRecordPlugin initDbConnection() {
          DruidPlugin druidPlugin = createDruidPlugin();
          ActiveRecordPlugin activeRecordPlugin = createActiveRecordPlugin(druidPlugin);
      
          druidPlugin.start();
          activeRecordPlugin.start();
      
          return activeRecordPlugin;
      }
      

   8. Define the ConfigInterceptor and ConfigHandler methods.

      Use these methods to perform global configurations during the system initialization.

      The sample code is as follows:

      @Override
      public void configInterceptor(Interceptors interceptors) {
      }
      
      @Override
      public void configHandler(Handlers handlers) {
      }
      

UserController.java

The UserController.java file uses the getData method to insert data into the database, query data from the database, and return the query result to the client in the JSON format. It uses the Db class of the JFinal framework to operate the database, and uses the custom User class to map the data, so as to return the data.

The code in the UserController.java file mainly includes the following parts:

1. Reference other classes and APIs.

   Declare this file to contain the following APIs and classes:

   • Controller class: processes requests and responses.
   • Db class: executes database operations.
   • Record class: operates the database, such as querying, inserting, updating, and deleting data.
   • ArrayList class: creates an empty list.
   • User class: maps database tables.
   • List API: operates the query result set.

   The sample code is as follows:

   import com.jfinal.core.Controller;
   import com.jfinal.plugin.activerecord.Db;
   import com.jfinal.plugin.activerecord.Record;
   
   import java.util.ArrayList;
   import java.util.List;
   

2. Define the UserController class.

   Use this class to provide a controller for the JFinal framework, and use the getData method to insert data into and query data from the database.

   1. Insert data. Create a dataList list that contains 10 Record objects. Each Record object has unique ID and USERNAME values. Use the Db.batchSave method to save the dataList list to a database table named TOMCAT_TEST.

      The sample code is as follows:

              for (int i = 0; i < 10; i++) {
                  Record record = new Record().set("ID", i).set("USERNAME", "Tomcat connection pool test" + i);
                  dataList.add(record);
              }
              Db.batchSave("TOMCAT_TEST", dataList, dataList.size());
      

   2. Query data. Use the Db.find method to execute an SQL query and store the query result in the resultList list. Use an enhanced FOR loop to traverse each Record object in the resultList list. Use the getStr method to obtain values of specified fields in a Record object and use the System.out.println method to return these values.

      The sample code is as follows:

          List<Record> resultList = Db.find("SELECT * FROM TOMCAT_TEST");
          for (Record result : resultList) {
              System.out.println(result.getStr("USERNAME"));
          }
      

   3. Modify data. Use a loop to perform 10 rounds of iterations and execute an update statement in each iteration. Call the Db.update method to update records in the TOMCAT_TEST table that meet the condition.

      The sample code is as follows:

          for (int i = 0; i < 10; i++) {
              Db.update("UPDATE TOMCAT_TEST SET USERNAME = 'Connection pool test" + i + "' WHERE ID = " + i);
          }
      

   4. Query the modified data. Query the TOMCAT_TEST table and save the query result in modifiedList. Return the information in the -----After modification----- section. Traverse modifiedList and return the USERNAME value of each record. Use the renderJson method to render the response message Data retrieved successfully into the JSON format and return it to the client.

      The sample code is as follows:

              List<Record> modifiedList = Db.find("SELECT * FROM TOMCAT_TEST");
              System.out.println("-----After modification-----");
              for (Record modified : modifiedList) {
                  System.out.println(modified.getStr("USERNAME"));
              }
              renderJson("Data retrieved successfully");
      

Introduction to the User.java file

The User.java file is used to map database tables and Java objects.

The code in the User.java file mainly includes the following parts:

1. Reference the Model class.

   Use the Model class to map database tables and operate data.

2. Define the User class.

   Use the User class to inherit the methods provided in the Model class for database operations.

   The sample code is as follows:

   import com.jfinal.plugin.activerecord.Model;
   
   
       public class User extends Model<User> {
           public static final User dao = new User();
   }
   

Full code

<?xml version="1.0" encoding="UTF-8"?>
<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.oceanbase</groupId>
    <artifactId>tomcat-mysql-client</artifactId>
    <version>1.0-SNAPSHOT</version>
    <!-- Packaging method (default to jar) -->
    <packaging>war</packaging>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>com.jfinal</groupId>
            <artifactId>jfinal</artifactId>
            <version>5.0.6</version>
        </dependency>


        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.2.8</version>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-dbcp2</artifactId>
            <version>2.9.0</version>
        </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.40</version>
            </dependency>

    </dependencies>
</project>

    #Apache Commons DBCP2 Connection Pool
    #Database Connection Pool Driver Class Name
    db.app.pool.driverClassName=com.mysql.jdbc.Driver
    #Database URL
    db.app.pool.url=jdbc:mysql:////host:port/schema_name?characterEncoding=UTF-8
    #Database username
    db.app.pool.username=user_name
    #Database password
    db.app.pool.password=******
    #Initial size of connection pool
    db.app.pool.initialSize=3
    #Maximum number of connections in the connection pool
    db.app.pool.maxTotal=10
    #Maximum number of idle connections in the connection pool
    db.app.pool.maxIdle=20
    #Minimum number of idle connections in the connection pool
    db.app.pool.minIdle=5
    #Maximum wait time for obtaining connections (in milliseconds)
    db.app.pool.maxWaitMillis=5000
    #Verify the connection's query statement
    db.app.pool.validationQuery=select 1

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
    <filter>
        <filter-name>jfinal</filter-name>
        <filter-class>com.jfinal.core.JFinalFilter</filter-class>
        <init-param>
            <param-name>configClass</param-name>
            <!-- your jfinal configuration location -->
            <param-value>com.oceanbase.testjfinal.config.UserConfig</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>jfinal</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

package com.oceanbase.testtomcat.config;

import com.alibaba.druid.filter.stat.StatFilter;
import com.alibaba.druid.util.JdbcConstants;
import com.alibaba.druid.wall.WallFilter;
import com.jfinal.config.*;
import com.jfinal.kit.PropKit;
import com.jfinal.plugin.activerecord.ActiveRecordPlugin;
import com.jfinal.plugin.activerecord.Db;
import com.jfinal.plugin.activerecord.dialect.MysqlDialect;
import com.jfinal.plugin.druid.DruidPlugin;
import com.jfinal.template.Engine;
import com.oceanbase.testtomcat.controller.UserController;
import com.oceanbase.testtomcat.pojo.User;

public class UserConfig extends JFinalConfig {
    @Override
    public void configConstant(Constants constants) {
        // Read properties configuration
        PropKit.use("application.properties");
    }

    @Override
    public void configRoute(Routes routes) {
        // Set the default access page for project startup, which does not need to be set in the web.
        routes.add("/hello", UserController.class);

    }

    @Override
    public void configEngine(Engine engine) {
    }

    @Override
    public void configPlugin(Plugins plugins) {
        init();
        DruidPlugin druidPlugin = createDruidPlugin();
        plugins.add(druidPlugin);

        ActiveRecordPlugin activeRecordPlugin = createActiveRecordPlugin(druidPlugin);
        activeRecordPlugin.addMapping("TOMCAT_TEST", User.class);
        plugins.add(activeRecordPlugin);
    }

    private DruidPlugin createDruidPlugin() {
        DruidPlugin druidPlugin = new DruidPlugin(
                PropKit.get("db.app.pool.url"),
                PropKit.get("db.app.pool.username"),
                PropKit.get("db.app.pool.password"),
                PropKit.get("db.app.pool.driverClassName")
        );

        druidPlugin.addFilter(new StatFilter());
        WallFilter wallFilter = new WallFilter();
        wallFilter.setDbType(JdbcConstants.OCEANBASE);
        druidPlugin.addFilter(wallFilter);

        druidPlugin.setInitialSize(PropKit.getInt("db.app.pool.initialSize"));
        druidPlugin.setMaxPoolPreparedStatementPerConnectionSize(PropKit.getInt("db.app.pool.maxTotal"));
        druidPlugin.setTimeBetweenConnectErrorMillis(PropKit.getInt("db.app.pool.maxWaitMillis"));
        druidPlugin.setValidationQuery("select 1 from dual");

        return druidPlugin;
    }

    private ActiveRecordPlugin createActiveRecordPlugin(DruidPlugin druidPlugin) {
        ActiveRecordPlugin activeRecordPlugin = new ActiveRecordPlugin(druidPlugin);
        activeRecordPlugin.setDialect(new MysqlDialect());

        return activeRecordPlugin;
    }

    public void init() {
        ActiveRecordPlugin arp = initDbConnection();

        // Check if table exists
        boolean tableExists = Db.queryInt("SELECT COUNT(*) FROM information_schema.TABLES WHERE TABLE_SCHEMA = 'TEST' AND TABLE_NAME = 'TOMCAT_TEST'") > 0;

        // Drop table if it exists
        if (tableExists) {
            Db.update("DROP TABLE TOMCAT_TEST");
        }

        // Create table
        String sql = "CREATE TABLE TOMCAT_TEST (ID int, USERNAME varchar(50))";
        Db.update(sql);

        arp.stop();
    }
    private ActiveRecordPlugin initDbConnection() {
        DruidPlugin druidPlugin = createDruidPlugin();
        ActiveRecordPlugin activeRecordPlugin = createActiveRecordPlugin(druidPlugin);

        druidPlugin.start();
        activeRecordPlugin.start();

        return activeRecordPlugin;
    }

    @Override
    public void configInterceptor(Interceptors interceptors) {
    }

    @Override
    public void configHandler(Handlers handlers) {
    }
}

package com.oceanbase.testtomcat.controller;

import com.jfinal.core.Controller;
import com.jfinal.plugin.activerecord.Db;
import com.jfinal.plugin.activerecord.Record;

import java.util.ArrayList;
import java.util.List;

public class UserController extends Controller {

    public void getData() {
        try {
            List<Record> dataList = new ArrayList<>();
            // Insert data
            for (int i = 0; i < 10; i++) {
                Record record = new Record().set("ID", i).set("USERNAME", "Tomcat connection pool test" + i);
                dataList.add(record);
            }
            Db.batchSave("TOMCAT_TEST", dataList, dataList.size());
            // Query data
            List<Record> resultList = Db.find("SELECT * FROM TOMCAT_TEST");
            for (Record result : resultList) {
                System.out.println(result.getStr("USERNAME"));
            }
            // Modify data
            for (int i = 0; i < 10; i++) {
                Db.update("UPDATE TOMCAT_TEST SET USERNAME = 'Connection pool test" + i + "' WHERE ID = " + i);
            }
            // Query the modified data
            List<Record> modifiedList = Db.find("SELECT * FROM TOMCAT_TEST");
            System.out.println("-----After modification-----");
            for (Record modified : modifiedList) {
                System.out.println(modified.getStr("USERNAME"));
            }
            renderJson("Data retrieved successfully");
        } catch (Exception e) {
            e.printStackTrace();
            renderJson("Error occurred");
        }
    }
}

package com.oceanbase.testtomcat.pojo;

import com.jfinal.plugin.activerecord.Model;


    public class User extends Model<User> {
        public static final User dao = new User();

}

References

For more information about OceanBase Connector/J, see OceanBase JDBC driver.