Java Connector(JCO)环境的搭建：Step by step to download and configure JCO in your laptop
我的ABAP系统有个函数名叫ZDIS_GET_UPSELL_MATERIALS，输入一个customer ID和product ID，会输出为这对客户和product组合维护的一组Upsell product ID和描述信息。
测试如下：

下面是使用Java消费该函数的代码：

package jco;

import java.io.File;
import java.io.FileOutputStream;
import java.util.Properties;
import com.sap.conn.jco.JCoDestination;
import com.sap.conn.jco.JCoDestinationManager;
import com.sap.conn.jco.JCoException;
import com.sap.conn.jco.JCoFunction;
import com.sap.conn.jco.JCoParameterList;
import com.sap.conn.jco.JCoRepository;
import com.sap.conn.jco.JCoTable;
import com.sap.conn.jco.ext.DestinationDataProvider;

/**
 * basic examples for Java to ABAP communication  
 * See help: https://help.sap.com/saphelp_nwpi711/helpdata/en/48/70792c872c1b5ae10000000a42189c/frameset.htm
 */
public class StepByStepClient
{
    static String DESTINATION_NAME = "ABAP_AS_WITHOUT_POOL";
    static public final String ABAP_DURATION = "abapLayerDuration";
    static public final String UPSELL_PRODUCT = "upsellProducts";
    static public final String PRODUCT_ID = "productID";
    static public final String PRODUCT_TEXT = "productText";
    
    static private Properties prepareProperty(){
        Properties connectProperties = new Properties();
        connectProperties.setProperty(DestinationDataProvider.JCO_ASHOST, "ldcixcd.wdf.sap.corp");
        connectProperties.setProperty(DestinationDataProvider.JCO_SYSNR,  "00");
        connectProperties.setProperty(DestinationDataProvider.JCO_CLIENT, "111");
        connectProperties.setProperty(DestinationDataProvider.JCO_USER,   "WANGJER");
        connectProperties.setProperty(DestinationDataProvider.JCO_PASSWD, "Saptest1");
        connectProperties.setProperty(DestinationDataProvider.JCO_LANG,   "en");
        createDestinationDataFile(DESTINATION_NAME, connectProperties);
        connectProperties.setProperty(DestinationDataProvider.JCO_POOL_CAPACITY, "3");
        connectProperties.setProperty(DestinationDataProvider.JCO_PEAK_LIMIT,    "10");
        createDestinationDataFile(DESTINATION_NAME, connectProperties);
        return connectProperties;
    }
    
    static public void main(String[] arg) {
        createDestinationDataFile(DESTINATION_NAME, prepareProperty());
        
        JCoDestination destination = null;
        try {
            destination = JCoDestinationManager.getDestination(DESTINATION_NAME);
            JCoRepository repo = destination.getRepository();
            JCoFunction stfcConnection = repo.getFunction("ZDIS_GET_UPSELL_MATERIALS");

            JCoParameterList imports = stfcConnection.getImportParameterList();
        
            String customerID = "1000040";
            String materialID = "11";

            imports.setValue("IV_CUSTOMER_ID", customerID);
            imports.setValue("IV_MATERIAL_ID", materialID);

            stfcConnection.execute(destination);
        
            JCoParameterList exports = stfcConnection.getExportParameterList();
            
            // int result = exports.getInt("EV_RESULT");
            int abapDuration = exports.getInt("EV_DURATION");
            
            StringBuilder sb = new StringBuilder();
            sb.append("{ \"" + ABAP_DURATION + "\": " + abapDuration + ",");
            
            sb.append("\"" + UPSELL_PRODUCT + "\":[");
            
            JCoTable codes = exports.getTable("ET_MATERIALS");
            
            int row = codes.getNumRows();
            System.out.println("Total rows: " + row);
            
            System.out.println("ABAP duration: " + abapDuration);
            
            for( int i = 0; i < row; i++){
                codes.setRow(i);
                System.out.println(codes.getString("MATERIAL_ID") + '\t' + codes.getString("MATERIAL_TEXT"));
                sb.append("{\"" + PRODUCT_ID + "\":" + codes.getString("MATERIAL_ID") + ","
                        + "\"" + PRODUCT_TEXT + "\":\"" + codes.getString("MATERIAL_TEXT") + "\"");
                if( i < row - 1){
                    sb.append("},");
                }
                else{
                    sb.append("}");
                }
            }
            sb.append("]}");
            
            System.out.println("Final json: " + sb.toString());
            
        } catch (JCoException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
    
    static private void createDestinationDataFile(String destinationName, Properties connectProperties)
    {
        File destCfg = new File(destinationName+".jcoDestination");
        try
        {
            FileOutputStream fos = new FileOutputStream(destCfg, false);
            connectProperties.store(fos, "for tests only !");
            fos.close();
        }
        catch (Exception e)
        {
            throw new RuntimeException("Unable to create the destination files", e);
        }
    } 
}

为简单起见没有使用Google的gson库进行Json的序列化。
执行结果：

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