Dinesh on Java

public int createEmployee(String name, int age, Long salary) {
 String insert_sql = "INSERT INTO EMPLOYEE ('name', 'age', 'salary') VALUES(?,?,?)";
 JdbcTemplate jt = getJdbcTemplate() ;
 Object[] params = new Object[]{name, age, salary};
 int ret = jt.update(insert_sql, params) ;
 throw new RuntimeException("simulate Error condition') ;
 return ret ;
 }

In this method, would you expect the insert to be committed to the database ? The answer is Yes, though that is not the desirable behavior. The default behaviour of JDBC is autocommit = true , which means, each insert or update is committed immediately. You could set autocommit = false and explicitly commit or rollback at the end of the method. But it is much easier to let your container handle this.

To add declarative transaction management to the above method use the following steps:
Step 1: Define a transaction manager in spring.xml

<bean class="org.springframework.jdbc.datasource.DataSourceTransactionManager" id="txManager"/>

Step 2: Turn on support for transaction annotations
Add to spring.xml

<tx:annotation-driven transaction-manager="txManager"/>

Step 3: Add the @Transactional annotation to the createEmployee Method

@Transactional
public int createEmployee(Employee employee) {
... 

Conceptually, calling a method on a transactional proxy looks like this…

Let us see how above mentioned steps work but before we begin, it is important to have at least one database tables on which we can perform various CRUD operations with the help of transactions. Let us take Employee table, which can be created in MySQL DAVDB database with the following DDL:

CREATE TABLE Employee(
   EMPID   INT NOT NULL AUTO_INCREMENT,
   NAME VARCHAR(26) NOT NULL,
   AGE  INT NOT NULL,
   SALARY BIGINT NOT NULL,
   PRIMARY KEY (EMPID)
);

1. Create a project with a name SpringTMDemo and create a package com.dineshonjava.sdnext under the src folder in the created project.

2. Add required Spring libraries using Add User Libs option as explained in the Spring Hello World Example chapter.
3. Add other required libraries mysql-connector-java.jar
4.Create DAO interface EmpDAO and list down all the required methods. Though it is not required and you can directly write EmployeeDaoImpl class, but as a good practice, let’s do it.
EmpDAO.java

package com.dineshonjava.sdnext.dao;

import java.util.List;

import com.dineshonjava.sdnext.domain.Employee;

/**
 * @author Dinesh Rajput
 *
 */
public interface EmpDao {
 
 /** 
  * This is the method to be used to create
  * a record in the Employee table.
  */
 void create(String name, Integer age, Long salary);
 /** 
  * This is the method to be used to list down
  * a record from the Employee table corresponding
  * to a passed Employee id.
  */
 Employee getEmployee(Integer empid);
 /** 
  * This is the method to be used to list down
  * all the records from the Employee table.
  */
 List listEmployees();
 /** 
  * This is the method to be used to delete
  * a record from the Employee table corresponding
  * to a passed Employee id.
  */
 void delete(Integer empid);
 /** 
  * This is the method to be used to update
  * a record into the Employee table.
  */
 void update(Integer empid, Integer age);
}

EmployeeDaoImpl.java

package com.dineshonjava.sdnext.dao.impl;

import java.util.List;

import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.support.JdbcDaoSupport;
import org.springframework.stereotype.Component;

import com.dineshonjava.sdnext.dao.EmpDao;
import com.dineshonjava.sdnext.domain.Employee;
import com.dineshonjava.sdnext.jdbc.utils.EmployeeMapper;

/**
 * @author Dinesh Rajput
 *
 */
@Component
public class EmployeeDaoImpl extends JdbcDaoSupport implements EmpDao {
// @Autowired
// private JdbcTemplate jdbcTemplateObject;
// 
// /**
//  * @param jdbcTemplateObject the jdbcTemplateObject to set
//  */
// public void setJdbcTemplateObject(JdbcTemplate jdbcTemplateObject) {
//  this.jdbcTemplateObject = jdbcTemplateObject;
// }

@Override
public void create(String name, Integer age, Long salary) {
  
try {
 String SQL = "INSERT INTO Employee (name, age, salary) VALUES (?, ?, ?)";
 getJdbcTemplate().update(SQL, new Object[]{name, age, salary} );
System.out.println("Created Record Name = " + name + " Age = " + age+ " Salary = " + salary);
 // to simulate the exception.
 throw new RuntimeException("simulate Error condition") ;
  } catch (DataAccessException e) {
       System.out.println("Error in creating record, rolling back");
       throw e;
    }
}

 @Override
 public Employee getEmployee(Integer empid) {
  String SQL = "SELECT * FROM Employee WHERE empid = ?";
  Employee employee = (Employee) getJdbcTemplate().queryForObject(SQL, new Object[]{empid}, new EmployeeMapper());
     return employee;
 }

 @Override
 public List listEmployees() {
  String SQL = "SELECT * FROM Employee";
  List employees = (List) getJdbcTemplate().query(SQL, new EmployeeMapper());
     return null;
 }

 @Override
 public void delete(Integer empid) {
  String SQL = "DELETE FROM Employee WHERE empid = ?";
  getJdbcTemplate().update(SQL, new Object[]{empid});
  System.out.println("Deleted Record with EMPID = " + empid );
 }

 @Override
 public void update(Integer empid, Integer age) {
   String SQL = "UPDATE Employee SET age = ? WHERE empid = ?";
   getJdbcTemplate().update(SQL, new Object[]{age, empid});
   System.out.println("Updated Record with EMPID = " + empid );
 }
}

5. Create other required Java classes Employee, EmployeeMapper and EmpMainApp under the com.dineshonjava.sdnext package. You can create rest of the POJO classes if required.
Employee.java

package com.dineshonjava.sdnext.domain;

/**
 * @author Dinesh Rajput
 *
 */
public class Employee {
 private int empid;
 private String name;
 private int age;
 private long salary;
 /**
  * @return the empid
  */
 public int getEmpid() {
  return empid;
 }
 /**
  * @param empid the empid to set
  */
 public void setEmpid(int empid) {
  this.empid = empid;
 }
 /**
  * @return the name
  */
 public String getName() {
  return name;
 }
 /**
  * @param name the name to set
  */
 public void setName(String name) {
  this.name = name;
 }
 /**
  * @return the age
  */
 public int getAge() {
  return age;
 }
 /**
  * @param age the age to set
  */
 public void setAge(int age) {
  this.age = age;
 }
 /**
  * @return the salary
  */
 public long getSalary() {
  return salary;
 }
 /**
  * @param salary the salary to set
  */
 public void setSalary(long salary) {
  this.salary = salary;
 }
 public String toString(){
  return "EMPLOYEE{empid- "+this.empid+" name- "+this.name+
    " age- "+this.age+" salary- "+this.salary+"}";
 }
}

EmployeeMapper.java

package com.dineshonjava.sdnext.jdbc.utils;

import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.jdbc.core.RowMapper;

import com.dineshonjava.sdnext.domain.Employee;

/**
 * @author Dinesh Rajput
 *
 */
public class EmployeeMapper implements RowMapper {  
 public Employee mapRow(ResultSet rs, int rowNum) throws SQLException {  
  Employee employee = new Employee();  
  employee.setEmpid(rs.getInt("empid"));  
  employee.setName(rs.getString("name"));  
  employee.setAge(rs.getInt("age"));  
  employee.setSalary(rs.getLong("salary"));  
  return employee;  
 }  
}  

EmpMainApp.java

package com.dineshonjava.sdnext.main;

import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.dineshonjava.sdnext.dao.EmpDao;
import com.dineshonjava.sdnext.domain.Employee;

/**
 * @author Dinesh Rajput
 *
 */
public class EmpMainApp {

 /**
  * @param args
  */
 public static void main(String[] args) {
  ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
  EmpDao empDao = (EmpDao) context.getBean("employeeDaoImpl");
  
  System.out.println("------Records Creation--------" );
  empDao.create("Raaz", 25, 50000l);
   
  System.out.println("------Listing Multiple Records--------" );
  List employees = empDao.listEmployees();
  for (Employee employee : employees) {
          System.out.print(employee);
     }
 }
}

6. Create Beans configuration file spring.xml under the src folder.

<beans xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p" xmlns:>
Once you are done with creating source and bean configuration files, let us run the application. If everything is fine with your application, this will print the following exception will be raised. In this case transaction will be rolled back and no record will be created in the database table.


Output:
Dec 12, 2012 11:59:23 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@1ed2ae8: display name [org.springframework.context.support.ClassPathXmlApplicationContext@1ed2ae8]; startup date [Wed Dec 12 23:59:23 IST 2012]; root of context hierarchy
Dec 12, 2012 11:59:23 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring.xml]
Dec 12, 2012 11:59:24 PM org.springframework.beans.factory.support.DefaultListableBeanFactory registerBeanDefinition
INFO: Overriding bean definition for bean 'employeeDaoImpl': replacing [Generic bean: class [com.dineshonjava.sdnext.dao.impl.EmployeeDaoImpl]; scope=singleton; abstract=false; lazyInit=false; autowireCandidate=true; autowireMode=0; dependencyCheck=0; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null] with [Generic bean: class [com.dineshonjava.sdnext.dao.impl.EmployeeDaoImpl]; scope=singleton; abstract=false; lazyInit=false; autowireCandidate=true; autowireMode=0; dependencyCheck=0; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in class path resource [spring.xml]]
Dec 12, 2012 11:59:24 PM org.springframework.context.support.AbstractApplicationContext obtainFreshBeanFactory
INFO: Bean factory for application context [org.springframework.context.support.ClassPathXmlApplicationContext@1ed2ae8]: org.springframework.beans.factory.support.DefaultListableBeanFactory@698403
Dec 12, 2012 11:59:24 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@698403: defining beans [org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,employeeDaoImpl,dataSource,txAdvice,org.springframework.aop.config.internalAutoProxyCreator,createOperation,org.springframework.aop.support.DefaultBeanFactoryPointcutAdvisor#0,transactionManager]; root of factory hierarchy
------Records Creation--------
Created Record Name = Raaz Age = 25 Salary = 50000
Exception in thread "main" java.lang.RuntimeException: simulate Error condition
at com.dineshonjava.sdnext.dao.impl.EmployeeDaoImpl.create(EmployeeDaoImpl.java:37)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:310)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:90)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy3.create(Unknown Source)
at com.dineshonjava.sdnext.main.EmpMainApp.main(EmpMainApp.java:25)


 

You can try above example after removing exception, and in this case it should commit the transaction and you should see a record in the database.

Rolling back:
The previous section outlined the basics of how to specify the transactional settings for the classes, typically service, DaoImpl layer classes, in your application in a declarative fashion. This section describes how you can control the rollback of transactions in a simple declarative fashion.

The recommended way to indicate to the Spring Framework's transaction infrastructure that a transaction's work is to be rolled back is to throw an Exception from code that is currently executing in the context of a transaction. The Spring Framework's transaction infrastructure code will catch any unhandled Exception as it bubbles up the call stack, and will mark the transaction for rollback.

However, please note that the Spring Framework's transaction infrastructure code will, by default, only mark a transaction for rollback in the case of runtime, unchecked exceptions; that is, when the thrown exception is an instance or subclass of RuntimeException. (Errors will also - by default - result in a rollback.) Checked exceptions that are thrown from a transactional method will not result in the transaction being rolled back.

Exactly which Exception types mark a transaction for rollback can be configured. Find below a snippet of XML configuration that demonstrates how one would configure rollback for a checked, application-specific Exception type.