interface ReportGenerator { 
 public void generate(Table table); 
} 
 
class ExcelGenerator implements ReportGenerator { 
 public void generate(Table table) { 
  System.out.println("generate an Excel report ..."); 
 } 
} 
 
class PDFGenerator implements ReportGenerator { 
 public void generate(Table table) { 
  System.out.println("generate an PDF report ..."); 
 } 
} 
 
class ReportService { 
 // 负责创建具体需要的报表生成器 
 private ReportGenerator generator = new PDFGenerator(); 
 // private static ReportGenerator generator = new ExcelGenerator(); 
  
 public void getDailyReport(Date date) { 
  table.setDate(date); 
  // ... 
  generator.generate(table); 
 } 
  
 public void getMonthlyReport(Month month) { 
  table.setMonth(month); 
  // ... 
  generator.generate(table); 
 } 
} 
 
 
public class Client { 
 public static void main(String[] args) { 
  ReportService reportService = new ReportService(); 
  reportService.getDailyReport(new Date()); 
  //reportService.getMonthlyReport(new Date()); 
 } 
} 

class Container { 
 // 以键-值对形式保存各种所需组件 Bean 
 private static Map<String, Object> beans; 
  
 public Container() { 
  beans = new HashMap<String, Object>(); 
   
  // 创建、保存具体的报表生起器 
  ReportGenerator reportGenerator = new PDFGenerator(); 
  beans.put("reportGenerator", reportGenerator); 
   
  // 获取、管理 ReportService 的引用 
  ReportService reportService = new ReportService(); 
  beans.put("reportService", reportService); 
 } 
  
 public static Object getBean(String id) { 
  return beans.get(id); 
 } 
} 
 
class ReportService { 
 // 消除紧耦合关系，由容器取而代之 
 // private static ReportGenerator generator = new PDFGenerator(); 
 private ReportGenerator generator = (ReportGenerator) Container.getBean("reportGenerator"); 
 
 public void getDailyReport(Date date) { 
  table.setDate(date); 
  generator.generate(table); 
 } 
  
 public void getMonthlyReport(Month month) { 
  table.setMonth(month); 
  generator.generate(table); 
 } 
} 
 
public class Client { 
 public static void main(String[] args) { 
  Container container = new Container(); 
  ReportService reportService = (ReportService)Container.getBean("reportService"); 
  reportService.getDailyReport(new Date()); 
  //reportService.getMonthlyReport(new Date()); 
 } 
} 

// 实际应用中可以是用 interface 来提供统一接口 
class ServiceLocator { 
 private static Container container = new Container(); 
  
 public static ReportGenerator getReportGenerator() { 
  return (ReportGenerator)container.getBean("reportGeneraator"); 
 } 
} 
 
class ReportService { 
 private ReportGenerator reportGenerator = ServiceLocator.getReportGenerator(); 
  
 // ... 
} 

class ReportService {
 // 消除紧耦合关系，由容器取而代之
 // private static ReportGenerator generator = new PDFGenerator();
 // 通过 Container..getBean("reportGenerator") ‘主动'查找
 private ReportGenerator generator = (ReportGenerator) Container
   .getBean("reportGenerator");

class ServiceLocator {
 privatestatic Container container = new Container(); 
 publicstatic ReportGenerator getReportGenerator() {
  // 还是container.getBean(), 用了委托而已
  return (ReportGenerator) container.getBean("reportGeneraator");
 }
} 
class ReportService {
 // ReportService 最终还是‘主动'查找，委托给ServiceLocator 而已
 private ReportGenerator reportGenerator = ServiceLocator.getReportGenerator(); 
}

import java.util.Date;
import java.util.HashMap;
import java.util.Map; 
// 为了能够编译运行，多了两个无关紧要的类
class Month { }
class Table {
 publicvoid setDate(Date date) { }
 publicvoid setMonth(Month month) { }
} 
// ------------ 以下均无甚重要改变 ----------------- //
interface ReportGenerator {
 publicvoid generate(Table table);
} 
class ExcelGenerator implements ReportGenerator { 
 public ExcelGenerator() {
  System.out.println("2...开始初始化 ExcelGenerator ...");
 } 
 publicvoid generate(Table table) {
  System.out.println("generate an Excel report ...");
 }
} 
class PDFGenerator implements ReportGenerator { 
 public PDFGenerator() {
  System.out.println("2...开始初始化 PDFGenerator ...");
 } 
 publicvoid generate(Table table) {
  System.out.println("generate an PDF report ...");
 }
}
//------------ 以上均无甚重要改变 ----------------- // 
class Container {
 // 以键-值对形式保存各种所需组件 Bean
 privatestatic Map<String, Object> beans; 
 public Container() {
  System.out.println("1...开始初始化 Container ..."); 
  beans = new HashMap<String, Object>(); 
  // 创建、保存具体的报表生起器
  ReportGenerator reportGenerator = new PDFGenerator();
  beans.put("reportGenerator", reportGenerator); 
  // 获取、管理 ReportService 的引用
  ReportService reportService = new ReportService();
  // 注入上面已创建的具体 ReportGenerator 实例
  reportService.setReportGenerator(reportGenerator);
  beans.put("reportService", reportService); 
  System.out.println("5...结束初始化 Container ...");
 } 
 publicstatic Object getBean(String id) {
  System.out.println("最后获取服务组件...getBean() --> " + id + " ...");
  returnbeans.get(id);
 }
}
 
class ReportService { 
 // private static ReportGenerator generator = new PDFGenerator();
 // 消除上面的紧耦合关系，由容器取而代之
 // private ReportGenerator generator = (ReportGenerator) Container
 //   .getBean("reportGenerator"); 
 // 去除上面的“主动”查找，提供私有字段来保存外部注入的对象
 private ReportGenerator generator; 
 // 以 setter 方式从外部注入
 publicvoid setReportGenerator(ReportGenerator generator) {
  System.out.println("4...开始注入 ReportGenerator ...");
  this.generator = generator;
 }
 
 private Table table = new Table(); 
 public ReportService() {
  System.out.println("3...开始初始化 ReportService ...");
 } 
 publicvoid getDailyReport(Date date) {
  table.setDate(date);
  generator.generate(table);
 } 
 publicvoid getMonthlyReport(Month month) {
  table.setMonth(month);
  generator.generate(table);
 }
}
 
publicclass Client {
 publicstaticvoid main(String[] args) {
  // 初始化容器
  new Container();
  ReportService reportService = (ReportService) Container
    .getBean("reportService");
  reportService.getDailyReport(new Date());
  // reportService.getMonthlyReport(new Date());
 }
}

1...开始初始化 Container ...
2...开始初始化 PDFGenerator ...
3...开始初始化 ReportService ...
4...开始注入 ReportGenerator ...
5...结束初始化 Container ...

最后获取服务组件...getBean() --> reportService ...
generate an PDF report ...