ioc dependency lookup

Author: zhaopengfei

.gitignore

@@ -21,3 +21,7 @@
 
 # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
 hs_err_pid*
+
+.idea/
+target/
+*.iml

spring-00-introduction/pom.xml

@@ -0,0 +1,24 @@
+<?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">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>me.erudev</groupId>
+    <artifactId>spring-00-introduction</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>javax.servlet-api</artifactId>
+            <version>3.1.0</version>
+        </dependency>
+    </dependencies>
+
+</project>

spring-00-introduction/src/main/java/me/erudev/architecture/dao/DemoDao.java

@@ -0,0 +1,11 @@
+package me.erudev.architecture.dao;
+
+import java.util.List;
+
+/**
+ * @author pengfei.zhao
+ * @date 2021/4/29 16:18
+ */
+public interface DemoDao {
+    List<String> findAll();
+}

spring-00-introduction/src/main/java/me/erudev/architecture/dao/impl/DemoDaoImpl.java

@@ -0,0 +1,19 @@
+package me.erudev.architecture.dao.impl;
+
+import me.erudev.architecture.dao.DemoDao;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * @author pengfei.zhao
+ * @date 2021/4/29 16:18
+ */
+public class DemoDaoImpl implements DemoDao {
+
+
+    @Override
+    public List<String> findAll() {
+        return Arrays.asList("aaa", "bbb", "ccc");
+    }
+}

spring-00-introduction/src/main/java/me/erudev/architecture/factory/BeanFactory.java

@@ -0,0 +1,42 @@
+package me.erudev.architecture.factory;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+
+/**
+ * @author pengfei.zhao
+ * @date 2021/4/29 16:34
+ */
+public class BeanFactory {
+    private static Properties properties;
+
+    private static Map<String, Object> cachedMap = new HashMap<>();
+
+    static {
+        properties = new Properties();
+        try {
+            properties.load(BeanFactory.class.getClassLoader().getResourceAsStream("factory.properties"));
+        } catch (IOException e) {
+            throw new ExceptionInInitializerError("BeanFactory initialize error:" + e.getMessage());
+        }
+    }
+
+    public static Object getBean(String beanName) {
+        if (!cachedMap.containsKey(beanName)) {
+            synchronized (BeanFactory.class) {
+                if (!cachedMap.containsKey(beanName)) {
+                    try {
+                        Class clazz = Class.forName(properties.getProperty(beanName));
+                        Object obj = clazz.newInstance();
+                        cachedMap.put(beanName, obj);
+                    } catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {
+                        e.printStackTrace();
+                    }
+                }
+            }
+        }
+        return cachedMap.get(beanName);
+    }
+}

spring-00-introduction/src/main/java/me/erudev/architecture/package-info.java

@@ -0,0 +1,5 @@
+/**
+ * @author pengfei.zhao
+ * @date 2021/4/29 16:01
+ */
+package me.erudev.architecture;

spring-00-introduction/src/main/java/me/erudev/architecture/service/DemoService.java

@@ -0,0 +1,12 @@
+package me.erudev.architecture.service;
+
+import java.util.List;
+
+/**
+ * @author pengfei.zhao
+ * @date 2021/4/29 16:18
+ */
+public interface DemoService {
+
+    List<String> findAll();
+}

spring-00-introduction/src/main/java/me/erudev/architecture/service/impl/DemoServiceImpl.java

@@ -0,0 +1,28 @@
+package me.erudev.architecture.service.impl;
+
+import me.erudev.architecture.dao.DemoDao;
+import me.erudev.architecture.factory.BeanFactory;
+import me.erudev.architecture.service.DemoService;
+
+import java.util.List;
+
+/**
+ * @author pengfei.zhao
+ * @date 2021/4/29 16:19
+ */
+public class DemoServiceImpl implements DemoService {
+
+    DemoDao demoDao = (DemoDao) BeanFactory.getBean("demoDao");
+
+    public DemoServiceImpl() throws ClassNotFoundException {
+        for (int i = 0; i < 10; i++) {
+            DemoDao demoDao = (DemoDao)BeanFactory.getBean("demoDao");
+            System.out.println(demoDao);
+        }
+    }
+
+    @Override
+    public List<String> findAll() {
+        return demoDao.findAll();
+    }
+}

spring-00-introduction/src/main/java/me/erudev/architecture/servlet/DemoServlet.java

@@ -0,0 +1,26 @@
+package me.erudev.architecture.servlet;
+
+import me.erudev.architecture.dao.DemoDao;
+import me.erudev.architecture.factory.BeanFactory;
+
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+/**
+ * @author pengfei.zhao
+ * @date 2021/4/29 16:22
+ */
+@WebServlet(urlPatterns = "/demo")
+public class DemoServlet extends HttpServlet {
+
+    DemoDao demoDao = (DemoDao) BeanFactory.getBean("demoDao");
+
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        resp.getWriter().println(demoDao.findAll().toString());
+    }
+}

spring-00-introduction/src/main/resources/factory.properties

@@ -0,0 +1,2 @@
+demoDao=me.erudev.architecture.dao.impl.DemoDaoImpl
+demoService=me.erudev.architecture.service.impl.DemoServiceImpl