thread local 学习笔记

thread local(thread 的局部变量)解决多线程并发,为每个使用该变量的线程提供独


立的副本,


jdk5.0后，threadlocal支持泛型
接口方法：


//设置当前线程中局部变量的值
void set(Object value)


//返回当前线程对应的局部变量
public Object get()


//删除当前线程局部变量的值
public  void remove()


//返回当前线程局部变量的初始值
protected Object initialValue()






示例程序
所需jar 包
commons-logging-1.1.1.jar
junit-4.10.jar
log4j-1.2.15.jar
log4jdbc4-1.2.jar
mysql-connector-java-5.1.7-bin.jar
slf4j-api-1.6.1.jar
slf4j-log4j12-1.6.1.jar

/*==============================================================*/
/* DBMS name:      MySQL 5.0                                    */
/* Created on:     2012-11-8 11:58:12                           */
/*==============================================================*/




drop table if exists t_classroom;


drop table if exists t_student;


drop table if exists t_student_classroom;


/*==============================================================*/
/* Table: t_classroom                                           */
/*==============================================================*/
create table t_classroom
(
   roomid               varchar(16) not null,
   roomname             varchar(16),
   primary key (roomid)
);


/*==============================================================*/
/* Table: t_student                                             */
/*==============================================================*/
create table t_student
(
   sno                  varchar(8) not null,
   sname                varchar(16),
   sage                 int,
   gender               varchar(16),
   sbrith               date,
   primary key (sno)
);


/*==============================================================*/
/* Table: t_student_classroom                                   */
/*==============================================================*/
create table t_student_classroom
(
   sno                  varchar(8) not null,
   roomid               varchar(16) not null,
   primary key (sno, roomid)
);


alter table t_student_classroom add constraint FK_fk_roomid foreign key (roomid)
      references t_classroom (roomid) on delete restrict on update restrict;


alter table t_student_classroom add constraint FK_fk_sno foreign key (sno)
      references t_student (sno) on delete restrict on update restrict;




示例代码如下:
/**
 * 教室
 * 
 * @time 下午2:41:21
 * @author retacn yue
 * @Email [email protected]
 */
public class ClassRoom {
private String classRoomId;
private String classRoomName;


public String getClassRoomId() {
return classRoomId;
}


public void setClassRoomId(String classRoomId) {
this.classRoomId = classRoomId;
}


public String getClassRoomName() {
return classRoomName;
}


public void setClassRoomName(String classRoomName) {
this.classRoomName = classRoomName;
}


}




/**
 * 学生
 * 
 * @time 下午2:40:57
 * @author retacn yue
 * @Email [email protected]
 */
public class Student {
private String sNo;
private String sName;
private String sAge;
private String gender;
private String sBirth;
private String classRoomId;
private String classRoomName;


public String getsNo() {
return sNo;
}


public void setsNo(String sNo) {
this.sNo = sNo;
}


public String getsName() {
return sName;
}


public void setsName(String sName) {
this.sName = sName;
}


public String getsAge() {
return sAge;
}


public void setsAge(String sAge) {
this.sAge = sAge;
}


public String getGender() {
return gender;
}


public void setGender(String gender) {
this.gender = gender;
}


public String getsBirth() {
return sBirth;
}


public void setsBirth(String sBirth) {
this.sBirth = sBirth;
}


public String getClassRoomId() {
return classRoomId;
}


public void setClassRoomId(String classRoomId) {
this.classRoomId = classRoomId;
}


public String getClassRoomName() {
return classRoomName;
}


public void setClassRoomName(String classRoomName) {
this.classRoomName = classRoomName;
}


}




dao层=========================================================


/**
 * 教室dao接口
 * 
 * @time 下午2:48:13
 * @author retacn yue
 * @Email [email protected]
 */
public interface ClassRoomDao {
public void addStudentRoom(String roomid, String sNo) throws 


Exception;
}






public class ClassRoomDaoImpl implements ClassRoomDao {


/**
* 添加教室
*/
@Override
public void addStudentRoom(String roomid, String sNo) throws 


Exception {
Connection conn = null;
PreparedStatement pstmt = null;


conn = ConnectionManager.getConnection();
try {
pstmt = conn.prepareStatement("insert into 


t_student_classroom(roomid,sno)values(?,?)");
pstmt.setString(1, roomid);
pstmt.setString(2, sNo);
pstmt.executeUpdate();
} catch (SQLException e) {
throw new Exception("add studentClassRoom" + 


e.getMessage(), e);
// e.printStackTrace();
} finally {
try {
if (pstmt != null) {
pstmt.close();
pstmt = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}




/**
 * 学生dao接口
 * 
 * @time 下午2:46:30
 * @author retacn yue
 * @Email [email protected]
 */
public interface StudentDao {
public void addStudent(Student student) throws Exception;
}






public class StudentDaoImpl implements StudentDao {


/**
* 添加学生
*/
@Override
public void addStudent(Student student) throws Exception {


Connection conn = null;
PreparedStatement pstmt = null;


conn = ConnectionManager.getConnection();
try {
pstmt = conn.prepareStatement(" insert into 


t_student(sno, sname, sage, gender, sbrith) values (?,?,?,?,?)");
pstmt.setString(1, student.getsNo());
pstmt.setString(2, student.getsName());
pstmt.setString(3, student.getsAge());
pstmt.setString(4, student.getGender());
pstmt.setString(5, student.getsBirth());
pstmt.executeUpdate();
} catch (SQLException e) {
throw new Exception("add student " + e.getMessage


(), e);
// e.printStackTrace();
} finally {
try {
if (pstmt != null) {
pstmt.close();
pstmt = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}


}
}




service层===================================================
/**
 * 
 * @time 下午3:03:30
 * @author retacn yue
 * @Email [email protected]
 */
public interface StudentService {
public void addStudent(Student student);
}






/**
 * 
 * @time 下午3:04:46
 * @author retacn yue
 * @Email [email protected]
 */
public class StudentServiceImpl implements StudentService {


/**
* 添加学生
*/
@Override
public void addStudent(Student student) {
StudentDao studentDao = new StudentDaoImpl();
ClassRoomDao classRoomDao = new ClassRoomDaoImpl();


try {
// 开 启事务
ConnectionManager.BeginTrans(true);


studentDao.addStudent(student);
classRoomDao.addStudentRoom


(student.getClassRoomId(), student.getsNo());
// 提交事务
ConnectionManager.commit();
} catch (Exception e) {
// 回滚
ConnectionManager.rollback();
e.printStackTrace();
} finally {
try {
// 关闭联接
ConnectionManager.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}


}


工具类================================================
/**
 * 读取jdbc配置文件
 * 
 * @time 下午1:32:22
 * @author retacn yue
 * @Email [email protected]
 */
public class JdbcProperies {
@SuppressWarnings("unused")
private static Log logger = LogFactory.getLog


(JdbcProperies.class);


public static Properties getPropObjectFromFile() {
Properties properties = new Properties();
// 取得当前线程的类加载器
ClassLoader classLoader = Thread.currentThread


().getContextClassLoader();
URL url = classLoader.getResource("jdbc.properties");
if (url == null) {
classLoader = ClassLoader.getSystemClassLoader();
url = classLoader.getResource("jdbc.properties");
}
System.out.println("=======" + url);
File file = new File(url.getFile());
InputStream inputStream = null;


try {
inputStream = new FileInputStream(file);
properties.load(inputStream);
} catch (IOException e) {
properties = null;
e.printStackTrace();
} finally {


try {
if (inputStream != null) {
inputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}


return properties;


}
}




/**
 * 数据库连接工具类
 * 
 * @time 下午1:25:59
 * @author retacn yue
 * @Email [email protected]
 */
public class DBConnection {
private static Connection conn = null;
private static DBConnection instance = null;
private static Properties jdbcPro = null;
private static String driveName = null;
private static String userName = null;
private static String pwd = null;
private static String url = null;


/**
* 构造器
*/
private DBConnection() {
}


/**
* 读取配置文件
* 
* @return
*/
private static Properties getConfigFromPropertiesFile() {
Properties properties = null;
properties = JdbcProperies.getPropObjectFromFile();
return properties;
}


/**
* 初始化配置文件
*/
private static void initJdbcParameters(Properties properties) {
driveName = properties.getProperty("driver");
userName = properties.getProperty("user");
pwd = properties.getProperty("password");
url = properties.getProperty("url");
}


/**
* 取得connection对象
* 
* @return
*/
public static Connection getConnection() {
return conn;
}


/**
* 取得DBConnection对象(单例)
* 
* @return
* @throws Exception
*/
public synchronized static DBConnection getInstance() throws 


Exception {
if (instance == null) {
jdbcPro = getConfigFromPropertiesFile();
instance = new DBConnection();
}
initJdbcParameters(jdbcPro);
createConnection();
return instance;


}


/**
* 建立连接
* 
* @throws Exception
*/
private static void createConnection() throws Exception {
Class.forName(driveName);
conn = DriverManager.getConnection(url, userName, pwd);
}
}


/**
 * 
 * 数据据事务管理工具类
 * 
 * @time 下午1:22:41
 * @author retacn yue
 * @Email [email protected]
 */
@SuppressWarnings({ "rawtypes", "unchecked" })
public class ConnectionManager {
private static ThreadLocal tl = new ThreadLocal();
private static Connection conn = null;


/**
* 是否开启事务
* 
* @param beginTrans
* @throws Exception
*/
@SuppressWarnings({ "static-access" })
public static void BeginTrans(boolean beginTrans) throws Exception 


{
if (tl.get() == null || ((Connection) tl.get()).isClosed


()) {
conn = DBConnection.getInstance().getConnection();
if (beginTrans) {
conn.setAutoCommit(false);
}
tl.set(conn);
}
}


/**
* 取得connection对象
* 
* @return
*/
public static Connection getConnection() {
return (Connection) tl.get();
}


/**
* 关闭事务
* 
* @throws SQLException
*/
public static void close() throws SQLException {
try {
((Connection) tl.get()).setAutoCommit(true);
} catch (SQLException e) {
e.printStackTrace();
}
((Connection) tl.get()).close();
tl.set(null);
}


/**
* 提交
*/
public static void commit() {
try {
((Connection) tl.get()).commit();
} catch (SQLException e) {
e.printStackTrace();
}
try {
((Connection) tl.get()).setAutoCommit(true);
} catch (SQLException e) {
e.printStackTrace();
}
}


/**
* 回滚
*/
public static void rollback() {
try {
((Connection) tl.get()).rollback();
} catch (SQLException e) {
e.printStackTrace();
}
try {
((Connection) tl.get()).setAutoCommit(true);
} catch (SQLException e) {
e.printStackTrace();
}
}


}


配置文件==============================================
driver = com.mysql.jdbc.Driver
password = ******
url = jdbc:mysql://localhost:3306/threadlocal
user = root








hibernate 里的


getCurrentSession


在hibernate配置文件中需要声明
<!-- 启用session的线程本地化技术,将session绑定到当前的线程


,实现session的传播(service层面上实现事务管理)-->
<property 


name="current_session_context_class">thread</property>




openSession和getCurrentSession的区别
 openSession需要在finally中关闭
 getCurrentSession只需调用rollback和commit就可以


使用场景

service方法中如果对多个dao进行操作，可使用getCurrentSession

参考博客

http://blog.csdn.net/lifetragedy/article/details/7751059