JDG_004：JDG 6.3 Quick Start 例子学习：Carmart（Transactional）

运行环境：JBoss Data Grid 6.3.0

Carmart（Transactional）与Carmart基本一样，但是多了事务，不同于数据库事务，这里是内存级的事务。
Carmart（Transactional）只能运行在library mode下，因为目前只有library mode支持事务。

学习重点：

1. 事务是如何配置开启的？

@ApplicationScoped
public class JBossASCacheContainerProvider implements CacheContainerProvider {
    private Logger log = Logger.getLogger(this.getClass().getName());

    private BasicCacheContainer manager;

    public BasicCacheContainer getCacheContainer() {
        if (manager == null) {
            GlobalConfiguration glob = new GlobalConfigurationBuilder()
                .nonClusteredDefault() //Helper method that gets you a default constructed GlobalConfiguration, preconfigured for use in LOCAL mode
                .globalJmxStatistics().enable() //This method allows enables the jmx statistics of the global configuration.
                .jmxDomain("org.infinispan.carmart.tx")  //prevent collision with non-transactional carmart
                .build(); //Builds  the GlobalConfiguration object
            Configuration loc = new ConfigurationBuilder()
                .jmxStatistics().enable() //Enable JMX statistics
                .clustering().cacheMode(CacheMode.LOCAL) //Set Cache mode to LOCAL - Data is not replicated.
                .transaction().transactionMode(TransactionMode.TRANSACTIONAL).autoCommit(false) //Enable Transactional mode with autocommit false
                .lockingMode(LockingMode.OPTIMISTIC).transactionManagerLookup(new GenericTransactionManagerLookup()) //uses GenericTransactionManagerLookup - This is a lookup class that locate transaction managers in the most  popular Java EE application servers. If no transaction manager can be found, it defaults on the dummy transaction manager.
                .locking().isolationLevel(IsolationLevel.REPEATABLE_READ) //Sets the isolation level of locking
                .eviction().maxEntries(4).strategy(EvictionStrategy.LIRS) //Sets  4 as maximum number of entries in a cache instance and uses the LIRS strategy - an efficient low inter-reference recency set replacement policy to improve buffer cache performance
                .persistence().passivation(false).addSingleFileStore().purgeOnStartup(true) //Disable passivation and adds a SingleFileStore that is purged on Startup
                .build(); //Builds the Configuration object
            manager = new DefaultCacheManager(glob, loc, true);
            log.info("=== Using DefaultCacheManager (library mode) ===");
        }
        return manager;
    }

    @PreDestroy
    public void cleanUp() {
        manager.stop();
        manager = null;
    }
}


2. 事务是如何保证的？

@Model
public class CarManager {

    private Logger log = Logger.getLogger(this.getClass().getName());

    public static final String CACHE_NAME = "carcache";

    public static final String CAR_NUMBERS_KEY = "carnumbers";

    @Inject
    private CacheContainerProvider provider;

    /*
     * Injects the javax.transaction.UserTransaction - The TransactionManager lookup is configured on
     * JBossASCacheContainerProvider/TomcatCacheContainerProvider impl classes for CacheContainerProvider
     */
    @Inject
    private UserTransaction utx;

    private BasicCache carCache;

    private String carId;
    private Car car = new Car();

    public CarManager() {
    }

    public String addNewCar() {
        carCache = provider.getCacheContainer().getCache(CACHE_NAME);
        try {
            utx.begin();
            List carNumbers = getNumberPlateList(carCache);
            carNumbers.add(car.getNumberPlate());
            carCache.put(CAR_NUMBERS_KEY, carNumbers);
            carCache.put(CarManager.encode(car.getNumberPlate()), car);
            utx.commit();
        } catch (Exception e) {
            if (utx != null) {
                try {
                    utx.rollback();
                } catch (Exception e1) {
                }
            }
        }
        return "home";
    }

    public String addNewCarWithRollback() {
        boolean throwInducedException = true;
        carCache = provider.getCacheContainer().getCache(CACHE_NAME);
        try {
            utx.begin();
            List carNumbers = getNumberPlateList(carCache);
            carNumbers.add(car.getNumberPlate());
            // store the new list of car numbers and then throw an exception -> roll-back
            // the car number list should not be stored in the cache
            carCache.put(CAR_NUMBERS_KEY, carNumbers);
            if (throwInducedException)
                throw new RuntimeException("Induced exception");
            carCache.put(CarManager.encode(car.getNumberPlate()), car);
            utx.commit();
        } catch (Exception e) {
            if (utx != null) {
                try {
                    utx.rollback();
                    log.info("Rolled back due to: " + e.getMessage());
                } catch (Exception e1) {
                }
            }
        }
        return "home";
    }

    /**
     * Operate on a clone of car number list so that we can demonstrate transaction roll-back.
     */
    @SuppressWarnings("unchecked")
    private List getNumberPlateList(BasicCache carCacheLoc) {
        List result = null;
        List carNumberList = (List) carCacheLoc.get(CAR_NUMBERS_KEY);
        if (carNumberList == null) {
            result = new LinkedList();
        } else {
            result = new LinkedList(carNumberList);
        }
        return result;
    }

    public String showCarDetails(String numberPlate) {
        carCache = provider.getCacheContainer().getCache(CACHE_NAME);
        try {
            utx.begin();
            this.car = (Car) carCache.get(encode(numberPlate));
            utx.commit();
        } catch (Exception e) {
            if (utx != null) {
                try {
                    utx.rollback();
                } catch (Exception e1) {
                }
            }
        }
        return "showdetails";
    }

    public List getCarList() {
        List result = null;
        try {
            utx.begin();
            // retrieve a cache
            carCache = provider.getCacheContainer().getCache(CACHE_NAME);
            // retrieve a list of number plates from the cache
            result = getNumberPlateList(carCache);
            utx.commit();
        } catch (Exception e) {
            if (utx != null) {
                try {
                    utx.rollback();
                } catch (Exception e1) {
                }
            }
        }
        return result;
    }

    public String removeCar(String numberPlate) {
        carCache = provider.getCacheContainer().getCache(CACHE_NAME);
        try {
            utx.begin();
            carCache.remove(encode(numberPlate));
            List carNumbers = getNumberPlateList(carCache);
            carNumbers.remove(numberPlate);
            carCache.put(CAR_NUMBERS_KEY, carNumbers);
            utx.commit();
        } catch (Exception e) {
            if (utx != null) {
                try {
                    utx.rollback();
                } catch (Exception e1) {
                }
            }
        }
        return null;
    }

    public void setCarId(String carId) {
        this.carId = carId;
    }

    public String getCarId() {
        return carId;
    }

    public void setCar(Car car) {
        this.car = car;
    }

    public Car getCar() {
        return car;
    }

    public static String encode(String key) {
        try {
            return URLEncoder.encode(key, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
    }

    public static String decode(String key) {
        try {
            return URLDecoder.decode(key, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
    }
}