import java.io.Serializable; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; interface IConnection { public void query(String sql); } interface IDriver { public DIALECT getDialect(); public IConnection getConnection(); } public class Bridge { public static void main(String[] args) { DriverManager.registerDriver(new MySqlDriver()); IConnection mysql = DriverManager.getConnection(); mysql.query("select * from table"); DriverManager.registerDriver(new OracleDriver()); IConnection oracle = DriverManager.getConnection(DIALECT.ORACLE); oracle.query("insert into table"); IConnection db2 = DriverManager.getConnection(DIALECT.DB2); db2.query("update table"); } } enum DIALECT implements Serializable { MYSQL,ORACLE,DB2; } class DriverManager { private static Map<DIALECT, IDriver> drivers = new ConcurrentHashMap<DIALECT, IDriver>(); private static final DIALECT DEFAULT_DIALECT = DIALECT.MYSQL; private DriverManager() { } public static void registerDriver(IDriver driver) { drivers.put(driver.getDialect(), driver); } public static IConnection getConnection() { return getConnection(DEFAULT_DIALECT); } public static IConnection getConnection(DIALECT dialect) { IDriver driver = drivers.get(dialect); if (driver == null) throw new IllegalArgumentException("no driver register with " + dialect); return driver.getConnection(); } } class MySqlDriver implements IDriver { @Override public IConnection getConnection() { return new IConnection() { @Override public void query(String sql) { System.out.println("MySql query ('" + sql + "') is executing......"); } }; } @Override public DIALECT getDialect() { return DIALECT.MYSQL; } } class OracleDriver implements IDriver { @Override public IConnection getConnection() { return new IConnection() { @Override public void query(String sql) { System.out.println("Oracle query ('" + sql + "') is executing......"); } }; } @Override public DIALECT getDialect() { return DIALECT.ORACLE; } } class DB2Driver implements IDriver { @Override public IConnection getConnection() { return new IConnection() { @Override public void query(String sql) { System.out.println("DB2 query ('" + sql + "') is executing......"); } }; } @Override public DIALECT getDialect() { return DIALECT.DB2; } }
输出为:
MySql query ('select * from table') is executing......
Oracle query ('insert into table') is executing......
Exception in thread "main" java.lang.IllegalArgumentException: no driver register with DB2
* jdbc api使用bridge模式 Service / DAO
* bridge是在设计之初的模式,adapter是针对已有系统的代码。
* 通过对象组合的方式,Bridge模式把两个角色之间的继承关系改为了耦合的关系,从而使这两者可以
从容自若的各自独立的变化,这也是Bridge模式的本意。
public abstract class Abstraction {
protected Implementor implementor;
public Abstraction(Implementor implementor) {
this.implementor = implementor;
}
public void operation() {
implementor.operationImpl();
}
}
public interface Implementor {
public void operationImpl();
}
class ConcreteImplementorA implements Implementor {
@Override public void operationImpl() {
// 真正的实现
System.out.println("具体实现A");
}
}
class ConcreteImplementorB implements Implementor {
@Override public void operationImpl() {
// 真正的实现
System.out.println("具体实现B");
}
}
class RefinedAbstraction extends Abstraction {
public RefinedAbstraction(Implementor implementor) {
super(implementor);
}
@Override public void operation() {
//do someting
super.operation();
//do other thing
}
}
* Facade模式注重简化接口,Adapter模式注重转换接口,Bridge模式注重分离接口(抽象)与其实现,
Decorator模式注重稳定接口的前提下为对象扩展功能。