设计模式---职责分离

传统的controller + server + dao
A B C三个模块看上去是分离的，实际上8个模块之间存在相互依赖的关系，并不是一个高内聚而是一个低内聚的形式。

DIP（依赖反转）模式

设计一 低级组件和高级组件都作为具体类放在同一个包里面

public class StringProcessor { //具体类private final StringReader stringReader; //具体类private final StringWriter stringWriter; //具体类//通过构造函数来注入依赖组件public StringProcessor(StringReader stringReader, StringWriter stringWriter) {this.stringReader = stringReader;this.stringWriter = stringWriter;}public void readAndWrite() {stringWriter.write(stringReader.getValue());}//测试用例public static void main(String[] args) {StringReader sr = new StringReader();sr.read("1111111");StringWriter sw = new StringWriter();StringProcessor sp = new StringProcessor(sr,sw);sp.readAndWrite();}}

设计二 低级组件具体类与高级组件接口实现类放在同一程序包
面向接口设计编程

public interface StringProcessor {void readAndWrite(StringReader stringReader, StringWriter stringWriter);}

public class StringProcessorImpl implements StringProcessor {//通过接口传参来注入依赖组件@Overridepublic void readAndWrite(StringReader stringReader, StringWriter stringWriter) {stringWriter.write(stringReader.getValue());}public static void main(String[] args){StringReader sr = new StringReader();sr.read("222222");StringWriter sw = new StringWriter();StringProcessor sp = new StringProcessorImpl();sp.readAndWrite(sr,sw);}}

设计三： 低级组件接口类与高级组件接口实现类放在同一程序包中
将StringReader 和StringWriete 进行抽象

public interface StringReader {void read(String path);String getValue();}public interface StringWriter {void write(String value);}

原先的类型变为接口(抽线了出来）

public class StringProcessorImpl implements StringProcessor {//StringReader 是接口//StringWriter 是接口@Overridepublic void readAndWrite(StringReader stringReader, StringWriter stringWriter) {stringWriter.write(stringReader.getValue());}public static void main(String[] args) {StringReader sr = new StringReaderImpl();sr.read("333333");StringWriter sw = new StringWriterImpl();StringProcessor sp = new StringProcessorImpl();sp.readAndWrite(sr,sw);}}

设计四 低级组件接口与高级组件接口类放在不同包中
sprin 框架注入

public class SPTest {@Resourceprivate StringProcessor sp;@Resourceprivate StringReader sr;@Resourceprivate StringWriter sw;public void main(String[] args) {sr.read("444444");sp.readAndWrite(sr,sw);}}

分层

架构设计视角下的关注点分离更重视组件之间的分离，并通过一定的通信策略来保证架构内各个组件间的相互引用。