小傅哥，Java 面经手册 • 拿大厂Offer，更新28、29、30、31

.gitignore

@@ -2,3 +2,4 @@
 /interview-04/interview-04.iml
 /interview-07/interview-07.iml
 /interview-05/interview-05.iml
+/ApiTest/ApiTest.iml

ApiTest/src/test/java/org/itstack/interview/test/ApiTest.java

@@ -1,6 +1,7 @@
 package org.itstack.interview.test;
 
 import org.junit.Test;
+import sun.misc.Unsafe;
 
 /**
  * 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
@@ -9,9 +10,8 @@
  */
 public class ApiTest {
 
-    @Test
-    public void test_() {
-
+    public static void main(String[] args) {
+//        Unsafe.loadFence();
     }
 
 }

interview-31/pom.xml

@@ -0,0 +1,139 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>interview</artifactId>
+        <groupId>org.itstack</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>interview-31</artifactId>
+
+    <properties>
+        <!-- Common -->
+        <jdk.version>1.8</jdk.version>
+        <sourceEncoding>UTF-8</sourceEncoding>
+        <!-- Open Service -->
+        <commons-lang3.version>3.8.1</commons-lang3.version>
+        <fastjson.version>1.2.60</fastjson.version>
+        <junit.version>4.12</junit.version>
+        <logback.version>1.0.9</logback.version>
+        <slf4j.version>1.7.7</slf4j.version>
+        <spring.version>4.3.24.RELEASE</spring.version>
+        <servlet-api.version>2.5</servlet-api.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.aspectj</groupId>
+            <artifactId>aspectjweaver</artifactId>
+            <version>1.6.12</version>
+        </dependency>
+        <dependency>
+            <groupId>org.aspectj</groupId>
+            <artifactId>aspectjrt</artifactId>
+            <version>1.6.12</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
+        <dependency>
+            <groupId>com.alibaba</groupId>
+            <artifactId>fastjson</artifactId>
+            <version>${fastjson.version}</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/junit/junit -->
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>ch.qos.logback</groupId>
+            <artifactId>logback-classic</artifactId>
+            <version>${logback.version}</version>
+            <exclusions>
+                <exclusion>
+                    <artifactId>slf4j-api</artifactId>
+                    <groupId>org.slf4j</groupId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+            <version>${slf4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-core</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-test</artifactId>
+            <version>${spring.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context-support</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-beans</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-jdbc</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-aop</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-aspects</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-web</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-aspects</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-tx</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>servlet-api</artifactId>
+            <version>${servlet-api.version}</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
+</project>

interview-31/src/main/java/org/itstack/interview/Bean_A.java

@@ -0,0 +1,18 @@
+package org.itstack.interview;
+
+public class Bean_A {
+
+    private Bean_B bean_b;
+
+    public Bean_B getBean_b() {
+        return bean_b;
+    }
+
+    public void setBean_b(Bean_B bean_b) {
+        this.bean_b = bean_b;
+    }
+
+    public void sayHello(String name) {
+        System.out.println("hello, " + name);
+    }
+}

interview-31/src/main/java/org/itstack/interview/Bean_B.java

@@ -0,0 +1,18 @@
+package org.itstack.interview;
+
+public class Bean_B {
+
+    private Bean_A bean_a;
+
+    public Bean_A getBean_a() {
+        return bean_a;
+    }
+
+    public void setBean_a(Bean_A bean_a) {
+        this.bean_a = bean_a;
+    }
+
+    public void sayHello(String name) {
+        System.out.println("hello, " + name);
+    }
+}

interview-31/src/main/java/org/itstack/interview/MyAspect.java

@@ -0,0 +1,9 @@
+package org.itstack.interview;
+
+public class MyAspect {
+
+    public void before() {
+        System.out.println("前置增强处理...");
+    }
+
+}

interview-31/src/main/resources/spring-config-aop.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
+       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd"
+       default-autowire="byName">
+
+    <bean id="bean_a" class="org.itstack.interview.Bean_A">
+        <property name="bean_b" ref="bean_b"/>
+    </bean>
+
+    <bean id="bean_b" class="org.itstack.interview.Bean_B">
+        <property name="bean_a" ref="bean_a"/>
+    </bean>
+
+    <bean id="myAspect" class="org.itstack.interview.MyAspect"/>
+
+    <aop:config>
+        <aop:aspect ref="myAspect">
+            <aop:before method="before" pointcut="execution(public void org.itstack.interview.*.sayHello(..))"/>
+        </aop:aspect>
+    </aop:config>
+
+</beans>

interview-31/src/main/resources/spring-config.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"
+       default-autowire="byName">
+
+    <bean id="bean_a" class="org.itstack.interview.Bean_A">
+        <property name="bean_b" ref="bean_b"/>
+    </bean>
+
+    <bean id="bean_b" class="org.itstack.interview.Bean_B">
+        <property name="bean_a" ref="bean_a"/>
+    </bean>
+
+</beans>

interview-31/src/test/java/org/itstack/interview/test/ApiTest.java

@@ -0,0 +1,28 @@
+package org.itstack.interview.test;
+
+import org.itstack.interview.Bean_A;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+public class ApiTest {
+
+    private Logger logger = LoggerFactory.getLogger(ApiTest.class);
+
+    @Test
+    public void test_alias() {
+        BeanFactory beanFactory = new ClassPathXmlApplicationContext("spring-config.xml");
+        Bean_A bean_a = beanFactory.getBean("bean_a", Bean_A.class);
+        logger.info("获取 Bean 通过别名：{}", bean_a.getBean_b());
+    }
+
+    @Test
+    public void test_aop(){
+        BeanFactory beanFactory = new ClassPathXmlApplicationContext("spring-config-aop.xml");
+        Bean_A bean_a = beanFactory.getBean("bean_a", Bean_A.class);
+        logger.info("获取 Bean 通过别名：{}", bean_a.getBean_b());
+    }
+
+}

interview-31/src/test/java/org/itstack/interview/test/CircleTest.java

@@ -0,0 +1,64 @@
+package org.itstack.interview.test;
+
+import java.lang.reflect.Field;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class CircleTest {
+
+    private final static Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
+
+    public static void main(String[] args) throws Exception {
+        Class[] classes = {A.class, B.class};
+        for (Class clazz : classes) {
+            getBean(clazz);
+        }
+        System.out.println(getBean(B.class).getA());
+        System.out.println(getBean(A.class).getB());
+    }
+
+    private static <T> T getBean(Class<T> beanClass) throws Exception {
+        String beanName = beanClass.getSimpleName().toLowerCase();
+        if (singletonObjects.containsKey(beanName)) {
+            return (T) singletonObjects.get(beanName);
+        }
+
+        Object obj = beanClass.getDeclaredConstructor().newInstance();
+        singletonObjects.put(beanName, obj);
+
+        Field[] fields = obj.getClass().getDeclaredFields();
+        for (Field field : fields) {
+            field.setAccessible(true);
+            Class<?> fieldClass = field.getType();
+            String fieldBeanName = fieldClass.getSimpleName().toLowerCase();
+            field.set(obj, singletonObjects.containsKey(fieldBeanName) ? singletonObjects.get(fieldBeanName) : getBean(fieldClass));
+        }
+        return (T) obj;
+    }
+
+}
+
+class A {
+    private B b;
+
+    public B getB() {
+        return b;
+    }
+
+    public void setB(B b) {
+        this.b = b;
+    }
+}
+
+class B {
+    private A a;
+
+    public A getA() {
+        return a;
+    }
+
+    public void setA(A a) {
+        this.a = a;
+    }
+}

pom.xml

@@ -9,13 +9,13 @@
     <packaging>pom</packaging>
     <version>1.0-SNAPSHOT</version>
     <modules>
+        <module>ApiTest</module>
         <module>interview-04</module>
         <module>interview-05</module>
         <module>interview-07</module>
         <module>interview-08</module>
         <module>interview-09</module>
         <module>interview-10</module>
-        <module>ApiTest</module>
         <module>interview-11</module>
         <module>interview-12</module>
         <module>interview-13</module>
@@ -36,6 +36,10 @@
         <module>interview-01</module>
         <module>interview-02</module>
         <module>interview-03</module>
+        <module>interview-28</module>
+        <module>interview-29</module>
+        <module>interview-30</module>
+        <module>interview-31</module>
     </modules>
 
     <dependencies>