设计模式之模板方法模式

//抽象模板类
public abstract class AbstractClass {
    //基本方法
    protected abstract void doSomething();

    //基本方法
    protected abstract void doAnything();

    public void templateMethod() {
        //调用基本方法，完成相关逻辑
        this.doAnything();
        this.doSomething();
    }
}

//具体模板类
public class ConcreteClass1 extends AbstractClass {
    @Override
    protected void doSomething() {
        //业务逻辑
    }

    @Override
    protected void doAnything() {
        //业务逻辑
    }
}

//具体模板类
public class ConcreteClass2 extends AbstractClass {
    @Override
    protected void doSomething() {
        //业务逻辑
    }

    @Override
    protected void doAnything() {
        //业务逻辑
    }
}

public class Client {
    public static void main(String[] args) {
        AbstractClass class1 = new ConcreteClass1();
        AbstractClass class2 = new ConcreteClass2();
        //调用模板方法
        class1.templateMethod();
        class2.templateMethod();
    }
}

public abstract class SimpleHttpServlet extends HttpServlet {

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {
        // 模板方法，定义了 HTTP 请求处理的骨架
        if (req.getMethod().equals("GET")) {
            doGet(req, resp);
        } else if (req.getMethod().equals("POST")) {
            doPost(req, resp);
        }
        // 其他 HTTP 方法的处理可以在这里扩展
    }

    protected abstract void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException;

    protected abstract void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException;
}

@Override
public final void init() throws ServletException {

    // Set bean properties from init parameters.
    PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
    if (!pvs.isEmpty()) {
        try {
            BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
            ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
            bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
            initBeanWrapper(bw);
            bw.setPropertyValues(pvs, true);
        }
        catch (BeansException ex) {
            if (logger.isErrorEnabled()) {
                logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
            }
            throw ex;
        }
    }

    // Let subclasses do whatever initialization they like.
    initServletBean();
}

protected void initServletBean() throws ServletException {
}

public abstract class InputStream {
    // 模板方法
    public int read(byte b[], int off, int len) throws IOException {
        // ...
        int c = read();
        // ...
        return c;
    }

    // 抽象方法，由子类提供具体实现
    public abstract int read() throws IOException;
}

public abstract class AbstractController implements Controller {
    // 模板方法
    @Override
    protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) {
        // 具体的请求处理逻辑由子类实现
        // ...
        return getModelAndView(request, response);
    }

    // 具体的请求处理逻辑由子类实现
    protected abstract ModelAndView getModelAndView(HttpServletRequest request, HttpServletResponse response);
}