依赖倒置原则

src/main/java/top/fjy8018/designpattern/principle/dependenceinversion/after/DCourse.java

@@ -0,0 +1,13 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+/**
+ * 学习课程接口
+ * 接口作为抽象存在，成为一个契约
+ * 面向抽象编程比面向具体实现细节编程实现简单，灵活度高
+ *
+ * @author F嘉阳
+ * @date 2018-09-18 17:19
+ */
+public interface DCourse {
+    void study();
+}

src/main/java/top/fjy8018/designpattern/principle/dependenceinversion/after/JavaDCourse.java

@@ -0,0 +1,17 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 课程都面向接口，满足依赖倒置原则：高层次的模块不应该依赖于低层次的模块，他们都应该依赖于抽象
+ *
+ * @author F嘉阳
+ * @date 2018-09-18 17:19
+ */
+@Slf4j
+public class JavaDCourse implements DCourse {
+    @Override
+    public void study() {
+        log.info("学习Java课程");
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/dependenceinversion/after/PythonDCourse.java

@@ -0,0 +1,17 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 所有课程实现类后面都不应该修改，添加新课程则增加新实现类，满足开闭原则
+ *
+ * @author F嘉阳
+ * @date 2018-09-18 17:19
+ */
+@Slf4j
+public class PythonDCourse implements DCourse {
+    @Override
+    public void study() {
+        log.info("学习Python课程");
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/dependenceinversion/after/Student.java

@@ -0,0 +1,17 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+/**
+ * @author F嘉阳
+ * @date 2018-09-18 17:20
+ */
+public class Student {
+
+    /**
+     * 具体学习哪个课程，交给高层模块通过参数注入
+     *
+     * @param course 课程
+     */
+    public void studyCourse(DCourse course) {
+        course.study();
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/dependenceinversion/after/Student2.java

@@ -0,0 +1,23 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+/**
+ * 构造器注入课程
+ *
+ * @author F嘉阳
+ * @date 2018-09-18 17:40
+ */
+public class Student2 {
+
+    private DCourse dCourse;
+
+    public Student2(DCourse dCourse) {
+        this.dCourse = dCourse;
+    }
+
+    /**
+     * 具体学习哪个课程，交给高层模块通过构造器注入
+     */
+    public void studyCourse() {
+        dCourse.study();
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/dependenceinversion/after/Student3.java

@@ -0,0 +1,26 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+/**
+ * Setter注入课程
+ *
+ * @author F嘉阳
+ * @date 2018-09-18 17:40
+ */
+public class Student3 {
+
+    private DCourse dCourse;
+
+    public Student3() {
+    }
+
+    /**
+     * 具体学习哪个课程，交给高层模块通过构造器注入
+     */
+    public void studyCourse() {
+        dCourse.study();
+    }
+
+    public void setdCourse(DCourse dCourse) {
+        this.dCourse = dCourse;
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/dependenceinversion/after/VueDCourse.java

@@ -0,0 +1,15 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * @author F嘉阳
+ * @date 2018-09-18 17:19
+ */
+@Slf4j
+public class VueDCourse implements DCourse {
+    @Override
+    public void study() {
+        log.info("学习Vue课程");
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/dependenceinversion/before/Student.java

@@ -0,0 +1,28 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.before;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 低层模块（模块被调用方）
+ * <p>
+ * 此时如果要加一个课程，必须修改该类
+ * 而对低层模块的修改应该尽量避免
+ *
+ * @author F嘉阳
+ * @date 2018-09-18 17:14
+ */
+@Slf4j
+public class Student {
+
+    public void studyJavaCourse() {
+        log.info("学习Java课程");
+    }
+
+    public void studyPythonCourse() {
+        log.info("学习Python课程");
+    }
+
+    public void studyVueCourse() {
+        log.info("学习Vue课程");
+    }
+}

src/test/java/top/fjy8018/designpattern/principle/dependenceinversion/after/Student2Test.java

@@ -0,0 +1,18 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * 依赖倒置构造器实现实现后单元测试
+ * 高层模块
+ */
+class Student2Test {
+
+    @Test
+    void study() {
+        Student2 student = new Student2(new JavaDCourse());
+        student.studyCourse();
+    }
+}

src/test/java/top/fjy8018/designpattern/principle/dependenceinversion/after/Student3Test.java

@@ -0,0 +1,25 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * 依赖倒置Setter实现实现后单元测试
+ * 高层模块
+ */
+class Student3Test {
+
+    @Test
+    void study() {
+        Student3 student = new Student3();
+        student.setdCourse(new JavaDCourse());
+        student.studyCourse();
+
+        student.setdCourse(new PythonDCourse());
+        student.studyCourse();
+
+        student.setdCourse(new VueDCourse());
+        student.studyCourse();
+    }
+}

src/test/java/top/fjy8018/designpattern/principle/dependenceinversion/after/StudentTest.java

@@ -0,0 +1,26 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.after;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * 依赖倒置接口方法实现后单元测试
+ * 高层模块
+ */
+class StudentTest {
+
+    /**
+     * 修改后高层不依赖低层模块{@link Student}的实现
+     * 此时如果高层模块要学多一门课程
+     * 则不需要修改Student，直接增加一个实现{@link DCourse} 的接口课程即可
+     * 实现了高层模块与低层模块的解耦
+     */
+    @Test
+    void study() {
+        Student student = new Student();
+        student.studyCourse(new JavaDCourse());
+        student.studyCourse(new PythonDCourse());
+        student.studyCourse(new VueDCourse());
+    }
+}

src/test/java/top/fjy8018/designpattern/principle/dependenceinversion/before/StudentTest.java

@@ -0,0 +1,26 @@
+package top.fjy8018.designpattern.principle.dependenceinversion.before;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * 依赖倒置实现前单元测试
+ * 高层模块（模块调用方）
+ */
+class StudentTest {
+
+    /**
+     * 此时存在的问题：
+     * 如果高层模块要学多一门课程
+     * 则低层模块{@link Student} 也要对应修改，即存在高层模块依赖低层模块，面向具体实现类编程
+     */
+    @Test
+    public void study() {
+        Student student = new Student();
+        student.studyJavaCourse();
+        student.studyPythonCourse();
+        student.studyVueCourse();
+    }
+
+}

src/test/java/top/fjy8018/designpattern/principle/openclose/JavaCourseTest.java

@@ -2,15 +2,15 @@ package top.fjy8018.designpattern.principle.openclose;
 
 import lombok.extern.slf4j.Slf4j;
 import org.junit.jupiter.api.Test;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
+import java.io.PrintStream;
 import java.math.BigDecimal;
 
-import static org.junit.jupiter.api.Assertions.*;
 
 /**
  * 开闭原则单元测试
+ *
+ * 由于底层通过加锁实现，故生产环境严禁使用{@link PrintStream#println(String)}
  */
 @Slf4j
 class JavaCourseTest {