Fuse ESB Enterprise - EIP Transaction Guide -

Overview

The AccountService class provides a simple example of accessing a data source through JDBC. The methods in this class can be used inside a local transaction or inside a global (XA) transaction.

Database schema

The AccountService example requires a single database table, accounts, which has two columns: a name column (containing the account name), and an amount column (containing the dollar balance of the account). The required database schema can be created by the following SQL statement:

CREATE TABLE accounts (name VARCHAR(50), amount INT);

AccountService class

Example 21 shows the complete listing of the AccountService class, which uses the Spring JdbcTemplate class to access a JDBC data source.

Example 21. The AccountService Class

// Java
package org.fusesource.example.tx.xa;

import java.util.List;

import javax.sql.DataSource;


import org.apache.camel.Exchange;
import org.apache.camel.language.XPath;
import org.apache.log4j.Logger;
import org.springframework.jdbc.core.JdbcTemplate;


public class AccountService {
    private static Logger log = Logger.getLogger(AccountService.class);
    private JdbcTemplate jdbc;

    public AccountService() {
    }

    public void setDataSource(DataSource ds) {
        jdbc = new JdbcTemplate(ds);
    }

    public void credit(
            @XPath("/transaction/transfer/receiver/text()") String name,
            @XPath("/transaction/transfer/amount/text()") String amount
            )
    {
        log.info("credit() called with args name = " + name + " and amount = " + amount);
        int origAmount = jdbc.queryForInt(
                "select amount from accounts where name = ?",
                new Object[]{name}
        );
        int newAmount = origAmount + Integer.parseInt(amount);
        
        jdbc.update(
                "update accounts set amount = ? where name = ?",
                new Object[] {newAmount, name}
        );
    }
    
    public void debit(
            @XPath("/transaction/transfer/sender/text()") String name,
            @XPath("/transaction/transfer/amount/text()") String amount
            )
    {
        log.info("debit() called with args name = " + name + " and amount = " + amount);
        int iamount = Integer.parseInt(amount);
        if (iamount > 100) {
            throw new IllegalArgumentException("Debit limit is 100");
        }
        int origAmount = jdbc.queryForInt(
                "select amount from accounts where name = ?",
                new Object[]{name}
        );
        int newAmount = origAmount - Integer.parseInt(amount);
        if (newAmount < 0) {
            throw new IllegalArgumentException("Not enough in account");
        }
        
        jdbc.update(
                "update accounts set amount = ? where name = ?",
                new Object[] {newAmount, name}
        );
    }
    
    public void dumpTable(Exchange ex) {
        log.info("dump() called");
        List<?> dump = jdbc.queryForList("select * from accounts");
        ex.getIn().setBody(dump.toString());
    }
}

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