[boutique] using dynamic agent to realize unified transaction management II

DAO layer

• Interface

public interface DeptDao{
    
	int insert(Dept dept);
}
public interface EmpDao{
    
	int insert(Emp emp);
}

• Implementation class

public class DeptDaoImpl implements DeptDao{
    
	@Override
	public int insert(Dept dept){
    
		QueryRunner queryRunner = new QueryRunner(TransactionManager.getDataSource());
		// .......  The specific operation database realizes the operation of inserting data into the database table 
	}
}
public class EmpDaoImpl implements EmpDao{
    
	@Override
	public int insert(Emp emp){
    
		QueryRunner queryRunner = new QueryRunner(TransactionManager.getDataSource());
		// .......  The specific operation database realizes the operation of inserting data into the database table 
	}
}

Service layer

• Interface

public interface EmpService{
    
	/** *  Add employees at the same time , And the employee's Department  */
	int insert(Emp emp,Dept dept);
}

• Implementation class

public class EmpServiceImpl{
    
	private DeptDao dpetDao = new DeptDaoImpl();
	private EmpDao empDao = new EmpDaoImpl();
	/** *  Add employees at the same time , And the employee's Department  */
	int insert(Emp emp,Dept dept){
    
		deptDao.insert(conn,dept);
		System.out.println(3/0);
		empDao.insert(conn,emp);
	}
}

Transaction manager

public class TransactionManager {
    
    private static DataSource dataSource;
    // Used to place... For local threads Connection Proxy object 
    private static ThreadLocal<Connection> proxyConnLocal = new ThreadLocal<>();
    // Used to place real... For local threads Connection object 
    private static ThreadLocal<Connection> realConnLocal = new ThreadLocal<>();

    static {
    
        Properties properties = new Properties();
        String propertiesFile = "/mysql.properties";
        try {
    
            InputStream is = TransactionManager.class.getResourceAsStream(propertiesFile);
            properties.load(is);
            dataSource = DruidDataSourceFactory.createDataSource(properties);
        } catch (IOException | ClassNotFoundException e) {
    
            e.printStackTrace();
        } catch (Exception e) {
    
            e.printStackTrace();
        }
    }
    private TransactionManager() {
    
    }

    /** *  Acquisition data source DataSource * * @return  If you need to start a transaction , return datasource Agent for , Otherwise, return to the original datasource */
  public static DataSource getDataSource() {
    
      DataSource ds = (DataSource) Proxy.newProxyInstance(dataSource.getClass().getClassLoader(), dataSource.getClass().getInterfaces(), new InvocationHandler() {
    
          @Override
          public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    
              if ("getConnection".equals(method.getName())) {
    
                  return proxyConnLocal.get();
              } else {
    
                  return method.invoke(proxy, args);
              }
          }
      });
      return ds;
  }

    /** *  Open transaction  * * @throws SQLException */
    public static void startTransaction() throws SQLException {
    
        Connection conn = dataSource.getConnection();
        // Set transactions not to be automatically committed 
        conn.setAutoCommit(false);
        // Will be real Connection Object into the local thread 
        realConnLocal.set(conn);
        // Open transaction 
        isTransactionEnabled.set(true);

        // Set up Connection Object does not close automatically 
        Connection proxyConn = (Connection) Proxy.newProxyInstance(conn.getClass().getClassLoader(), conn.getClass().getInterfaces(), new InvocationHandler() {
    
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    
                if ("close".equals(method.getName())) {
     //
                    return null;
                } else {
    
                    return method.invoke(conn, args);
                }
            }
        });
        // take Connection Put the proxy object into the local thread 
        proxyConnLocal.set(proxyConn);
    }

    /** *  Commit transaction  */
    public static void commitTransaction() {
    
        DbUtils.commitAndCloseQuietly(proxyConnLocal.get());
    }

    /** *  Roll back the transaction  */
    public static void rollbackTransaction() {
    
        DbUtils.rollbackAndCloseQuietly(proxyConnLocal.get());
    }

    public static void release() {
    
        DbUtils.closeQuietly(realConnLocal.get());
        realConnLocal.remove();
        proxyConnLocal.remove();
        isTransactionEnabled.remove();
    }
    
}

Dynamic agent transaction enhancement

public class ServiceProxy implements InvocationHandler {
    
    private Object service;

    public ServiceProxy(Object service) {
    
        this.service = service;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    
        Object res = null;
        // Whether the method is marked with transaction 
        try {
    
            TransactionManager.startTransaction();
            // Business methods 
            res = method.invoke(service, args);
            TransactionManager.commitTransaction();
        } catch (Exception e) {
    
            e.printStackTrace();
            TransactionManager.rollbackTransaction();
        } finally {
    
            TransactionManager.release();
        }
        return res;
    }

    public Object getProxy() {
    
        return Proxy.newProxyInstance(service.getClass().getClassLoader(), service.getClass().getInterfaces(), this);
    }

}

Test code

public static void main(String[] args) throws SQLException {
    
	Dept dept = new Dept(20,"ACCOUNTING","NEWYORK");
	Emp emp = new Emp(7369, "SMITH", "CLERK", 7902,LocalDate.of(1980, 12, 17), 800D, null, 20);
	EmpService empService = EmpServiceImpl();
    ServiceProxy serviceProxy = new ServiceProxy(empService);
    EmpService proxy = (EmpService) serviceProxy .getProxy();

    boolean addRes = proxy.add(emp,dept);
    System.out.println(addRes);
}

Existing problems

Using the technology introduced in this blog basically solves the unified management of affairs . But there is a small problem with the above code , That's how all execution DeptDao Of insert() and EmpDao Of insert() Methods will have transaction support , The specific solution is to True Add a local variable to identify whether you need to return the support transaction DataSource That's all right. . Explanation of this piece , See code ：https://gitee.com/hcshow/credits, There are detailed code explanations and application cases in the project .