Spring中的設計模式

時間 2019-12-11

標籤 spring 設計模式欄目 Spring 简体版

原文原文鏈接

設計模式分爲建立型、行爲型和結構型spring

設計模式的6大原則：express

　　一、開閉原則：對擴展開放，對修改關閉apache

　　二、里氏替換：任何父類出現的地方，子類均可以替換。子類不要重寫和重載父類的方法編程

　　三、接口隔離：接口最小化，實現的接口不該包含不須要的方法設計模式

　　四、依賴倒置：細節依賴抽象，抽象不該該依賴細節；依賴接口而不依賴具體的類app

　　五、迪米特原則：減小類之間的耦合，調用依賴類封裝好的方法，不對其進行修改less

　　六、單一職責：一個類只負責一項職責ide

　　七、合成複用：多用組合，少用繼承ui

一、建造者（Builder）模式this

　　建造者模式：又叫生成器模式。建造者模式能夠將一個產品的內部表象與產品的生成過程分割開來，從而能夠使一個建造過程生成具備不一樣的內部表象的產品對象。

　　若是咱們用了建造者模式，那麼用戶就只需指定須要建造的類型就能夠獲得它們，而具體建造的過程和細節就不需知道了。

　　角色：

　　建造者：Builder--抽象建造者類，即爲建立一個產品對象的各個部件指定的抽象接口。

　　具體建造者：實現Builder接口，構造和裝配各個組件。

　　指揮者：是構建一個使用Builder接口的對象，用來根據用戶的需求構建具體的對象。

在Spring中BeanDefinitionBuilder就是使用了建造者模式。容許咱們以編程的方式定義bean的類，爲AbstractBeanDefinition抽象類的相關實現設置值，好比做用域，

工廠方法，屬性等。

/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory.support;

import org.springframework.beans.factory.config.RuntimeBeanReference;
import org.springframework.util.ObjectUtils;

/**
 * Programmatic means of constructing
 * {@link org.springframework.beans.factory.config.BeanDefinition BeanDefinitions}
 * using the builder pattern. Intended primarily for use when implementing Spring 2.0
 * {@link org.springframework.beans.factory.xml.NamespaceHandler NamespaceHandlers}.
 *
 * @author Rod Johnson
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 2.0
 */
public class BeanDefinitionBuilder {/**
     * Create a new {@code BeanDefinitionBuilder} used to construct a {@link RootBeanDefinition}.
     * @param beanClassName the class name for the bean that the definition is being created for
     * @param factoryMethodName the name of the method to use to construct the bean instance
     */
    public static BeanDefinitionBuilder rootBeanDefinition(String beanClassName, String factoryMethodName) {
        BeanDefinitionBuilder builder = new BeanDefinitionBuilder();
        builder.beanDefinition = new RootBeanDefinition();
        builder.beanDefinition.setBeanClassName(beanClassName);
        builder.beanDefinition.setFactoryMethodName(factoryMethodName);
        return builder;
    }
/**
     * The {@code BeanDefinition} instance we are creating.
     */
    private AbstractBeanDefinition beanDefinition;

    /**
     * Our current position with respect to constructor args.
     */
    private int constructorArgIndex;


    /**
     * Enforce the use of factory methods.
     */
    private BeanDefinitionBuilder() {
    }

    /**
     * Return the current BeanDefinition object in its raw (unvalidated) form.
     * @see #getBeanDefinition()
     */
    public AbstractBeanDefinition getRawBeanDefinition() {
        return this.beanDefinition;
    }

    /**
     * Validate and return the created BeanDefinition object.
     */
    public AbstractBeanDefinition getBeanDefinition() {
        this.beanDefinition.validate();
        return this.beanDefinition;
    }

    /**
     * Set the name of the parent definition of this bean definition.
     */
    public BeanDefinitionBuilder setParentName(String parentName) {
        this.beanDefinition.setParentName(parentName);
        return this;
    }

    /**
     * Set the name of a static factory method to use for this definition,
     * to be called on this bean's class.
     */
    public BeanDefinitionBuilder setFactoryMethod(String factoryMethod) {
        this.beanDefinition.setFactoryMethodName(factoryMethod);
        return this;
    }

    /**
     * Set the name of a non-static factory method to use for this definition,
     * including the bean name of the factory instance to call the method on.
     * @since 4.3.6
     */
    public BeanDefinitionBuilder setFactoryMethodOnBean(String factoryMethod, String factoryBean) {
        this.beanDefinition.setFactoryMethodName(factoryMethod);
        this.beanDefinition.setFactoryBeanName(factoryBean);
        return this;
    }

    /**
     * Add an indexed constructor arg value. The current index is tracked internally
     * and all additions are at the present point.
     * @deprecated since Spring 2.5, in favor of {@link #addConstructorArgValue}.
     * This variant just remains around for Spring Security 2.x compatibility.
     */
    @Deprecated
    public BeanDefinitionBuilder addConstructorArg(Object value) {
        return addConstructorArgValue(value);
    }

    /**
     * Add an indexed constructor arg value. The current index is tracked internally
     * and all additions are at the present point.
     */
    public BeanDefinitionBuilder addConstructorArgValue(Object value) {
        this.beanDefinition.getConstructorArgumentValues().addIndexedArgumentValue(
                this.constructorArgIndex++, value);
        return this;
    }

    /**
     * Add a reference to a named bean as a constructor arg.
     * @see #addConstructorArgValue(Object)
     */
    public BeanDefinitionBuilder addConstructorArgReference(String beanName) {
        this.beanDefinition.getConstructorArgumentValues().addIndexedArgumentValue(
                this.constructorArgIndex++, new RuntimeBeanReference(beanName));
        return this;
    }

    /**
     * Add the supplied property value under the given name.
     */
    public BeanDefinitionBuilder addPropertyValue(String name, Object value) {
        this.beanDefinition.getPropertyValues().add(name, value);
        return this;
    }

    /**
     * Add a reference to the specified bean name under the property specified.
     * @param name the name of the property to add the reference to
     * @param beanName the name of the bean being referenced
     */
    public BeanDefinitionBuilder addPropertyReference(String name, String beanName) {
        this.beanDefinition.getPropertyValues().add(name, new RuntimeBeanReference(beanName));
        return this;
    }

    /**
     * Set the init method for this definition.
     */
    public BeanDefinitionBuilder setInitMethodName(String methodName) {
        this.beanDefinition.setInitMethodName(methodName);
        return this;
    }

    /**
     * Set the destroy method for this definition.
     */
    public BeanDefinitionBuilder setDestroyMethodName(String methodName) {
        this.beanDefinition.setDestroyMethodName(methodName);
        return this;
    }


    /**
     * Set the scope of this definition.
     * @see org.springframework.beans.factory.config.BeanDefinition#SCOPE_SINGLETON
     * @see org.springframework.beans.factory.config.BeanDefinition#SCOPE_PROTOTYPE
     */
    public BeanDefinitionBuilder setScope(String scope) {
        this.beanDefinition.setScope(scope);
        return this;
    }

    /**
     * Set whether or not this definition is abstract.
     */
    public BeanDefinitionBuilder setAbstract(boolean flag) {
        this.beanDefinition.setAbstract(flag);
        return this;
    }

    /**
     * Set whether beans for this definition should be lazily initialized or not.
     */
    public BeanDefinitionBuilder setLazyInit(boolean lazy) {
        this.beanDefinition.setLazyInit(lazy);
        return this;
    }

    /**
     * Set the autowire mode for this definition.
     */
    public BeanDefinitionBuilder setAutowireMode(int autowireMode) {
        beanDefinition.setAutowireMode(autowireMode);
        return this;
    }
...
}

二、工廠模式（靜態工廠方法）

　　這種模式容許經過使用靜態方法對象進行初始化，稱爲工廠方法。在Spring中，能夠經過指定的工廠方法建立bean。

　　如DefaultListableBeanFactory的

    @Override
    public <T> T getBean(Class<T> requiredType) throws BeansException {
        return getBean(requiredType, (Object[]) null);
    }

    @Override
    public <T> T getBean(Class<T> requiredType, Object... args) throws BeansException {
        NamedBeanHolder<T> namedBean = resolveNamedBean(requiredType, args);
        if (namedBean != null) {
            return namedBean.getBeanInstance();
        }
        BeanFactory parent = getParentBeanFactory();
        if (parent != null) {
            return parent.getBean(requiredType, args);
        }
        throw new NoSuchBeanDefinitionException(requiredType);
    }