hi Olaf

thank you for reply, 

yes, i had checked module.framework.system.packages.extra , "oracle.jdbc" is already in the list as default.

from tomcat-9.0.43\webapps\ROOT\WEB-INF\shielded-container-libportal-impl.jar\portal.properties

    module.framework.system.packages.extra=\
        com.ibm.crypto.provider,\
        com.ibm.db2.jcc,\
        com.microsoft.sqlserver.jdbc,\
        com.mysql.cj.jdbc,\
        com.mysql.jdbc,\
        com.p6spy.engine.spy,\
        com.sun.security.auth.module,\
        com.sybase.jdbc4.jdbc,\
        oracle.jdbc,\
        org.postgresql,\
        org.hsqldb.jdbc,\
        org.mariadb.jdbc,\
        sun.misc,\
        sun.net.util,\
        sun.security.provider,\
        \
        #
        # WebSocket Support
        #
        \
        com.ibm.websphere.wsoc,\
        io.undertow.websockets.jsr,\
        javax.websocket,\
        javax.websocket.server,\
        org.apache.tomcat.websocket.server,\
        weblogic.websocket.tyrus

i am sorry, i thought image will make it mare clear

my portlet

package com.ci.zt.portlet;

import com.ci.zt.constants.ZTestMVCPortletKeys;
import com.liferay.portal.kernel.portlet.bridges.mvc.MVCPortlet;

import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.portlet.Portlet;
import javax.portlet.PortletException;
import javax.portlet.RenderRequest;
import javax.portlet.RenderResponse;

import org.osgi.service.component.annotations.Component;

/**
 * @author vic.chen
 */
@Component(
    immediate = true,
    property = {
        "com.liferay.portlet.display-category=category.sample",
        "com.liferay.portlet.header-portlet-css=/css/main.css",
        "com.liferay.portlet.instanceable=true",
        "javax.portlet.display-name=ZTestMVC",
        "javax.portlet.init-param.template-path=/",
        "javax.portlet.init-param.view-template=/view.jsp",
        "javax.portlet.name=" + ZTestMVCPortletKeys.ZTESTMVC,
        "javax.portlet.resource-bundle=content.Language",
        "javax.portlet.security-role-ref=power-user,user"
    },
    service = Portlet.class
)
public class ZTestMVCPortlet extends MVCPortlet {
    
    @Override
    public void doView(RenderRequest renderRequest, RenderResponse renderResponse)
            throws IOException, PortletException {
        // TODO Auto-generated method stub
        super.doView(renderRequest, renderResponse);
        this.test();
        
    }

    
    public void test() {
        Statement stmt = null;
        ResultSet rs = null;
        try {
          Class.forName("oracle.jdbc.OracleDriver");
            Connection con = DriverManager.getConnection("jdbc:oracle:thin:@testhost:1521:test", "username", "password");
            stmt = con.createStatement();
            rs = stmt.executeQuery(MATERIAL_INFO("100-72-5000-00"));
            while (rs.next()) {
                System.out.println(rs.getString("CHILD_PART_NUMBER"));
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    public static String MATERIAL_INFO(String masterPartNumber) {
        StringBuffer sql = new StringBuffer();
        sql.append("SELECT ");
        sql.append(" ITEM.ITEM_NUMBER AS CHILD_PART_NUMBER ");
        sql.append("FROM AGILE.ITEM ITEM ");
        sql.append("WHERE 1=1 ");
        sql.append(" AND ITEM.ITEM_NUMBER = '").append(masterPartNumber).append("'");
        return sql.toString();
    }
    
    public static void main(String[] msg) {
        ZTestMVCPortlet plm=new ZTestMVCPortlet();
        plm.test();
    }
    
}

my build.gradle

dependencies {
    compileOnly group: "com.liferay.portal", name: "release.portal.api"

    cssBuilder group: "com.liferay", name: "com.liferay.css.builder", version: "3.0.2"
    runtime group: 'com.oracle.database.jdbc', name: 'ojdbc8', version: '21.3.0.0'
    
}

again, thank you for reply

Hi Antonio

thank you. have a nice day.

i put liferay-portal-database-all-in-one-support-1.2.1.jar in tomcat-9.0.43\webapps\ROOT\WEB-INF\lib, and put ojdbc8.jar in tomcat-9.0.43\webapps\ROOT\WEB-INF\shielded-container-lib

but i still got ClassNotFoundException in Class.forName("oracle.jdbc.OracleDriver");

my final goal is read external data via service builder(if the target is a database). and i tried both spring-bean and datasourceprovider. Unfortunately, they were all unable to succeed for different reasons.