package springdemo;

public class HelloBean {
  private String helloWorld;
  public String getHelloWorld() {
    return helloWorld;
  }
  public void setHelloWorld(String helloWorld) {
    this.helloWorld = helloWorld;
  }
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd" >
<beans>
　　<bean id="helloBean" class="springdemo.HelloBean">
　　　　<property name="helloWorld">
　　　　　　<value>Hello!chb!</value>
　　　　</property>
　　</bean>
</beans>

ApplicationContext context = new ClassPathXmlApplicationContext("bean_config.xml");
//这种用法不够灵活，不建议使用。
 HelloBean helloBean = (HelloBean)context.getBean("helloBean");
 System.out.println(helloBean.getHelloWorld());

public interface BeanFactory {
  public Object getBean(String id);
}

//实现类ClassPathXmlApplicationContext
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;

public class ClassPathXmlApplicationContext implements BeanFactory {
  
  private Map<String , Object> beans = new HashMap<String, Object>();
  
  //(IOC:Inverse of Control/DI:Dependency Injection)
  public ClassPathXmlApplicationContext() throws Exception {
    SAXBuilder sb=new SAXBuilder();
    
    Document doc=sb.build(this.getClass().getClassLoader().getResourceAsStream("beans.xml")); //构造文档对象
    Element root=doc.getRootElement(); //获取根元素HD
    List list=root.getChildren("bean");//取名字为disk的所有元素
    for(int i=0;i<list.size();i++){
      Element element=(Element)list.get(i);
      String id=element.getAttributeValue("id");
      String clazz=element.getAttributeValue("class");
      Object o = Class.forName(clazz).newInstance();
      System.out.println(id);
      System.out.println(clazz);
      beans.put(id, o);
      
      for(Element propertyElement : (List<Element>)element.getChildren("property")) {
        String name = propertyElement.getAttributeValue("name"); //userDAO
        String bean = propertyElement.getAttributeValue("bean"); //u
        Object beanObject = beans.get(bean);//UserDAOImpl instance
        
        String methodName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1);
        System.out.println("method name = " + methodName);
        
        Method m = o.getClass().getMethod(methodName, beanObject.getClass().getInterfaces()[0]);
        m.invoke(o, beanObject);
      }     
    }    
  }

  public Object getBean(String id) {
    return beans.get(id);
  }
}

ApplicationContext context = new ClassPathXmlApplicationContext("bean_config.xml");
HelloBean helloBean = (HelloBean)context.getBean("helloBean");

BeanFactory factory= new ClassPathXmlApplicationContext("bean_config.xml");
HelloBean helloBean = (HelloBean)factory.getBean("helloBean");

Resource rs = new FileSystemResource("D:/software/tomcat/webapps/springWebDemo/WEB-INF/classes/bean_config.xml");
BeanFactory factory = new XmlBeanFactory(rs);
HelloBean helloBean = (HelloBean)factory.getBean("helloBean");
System.out.println(helloBean.getHelloWorld());

helloBean.class=springdemo.HelloBean
helloBean.helloWorld=Hello!HelloWorld!

BeanDefinitionRegistry reg = new DefaultListableBeanFactory();
PropertiesBeanDefinitionReader reader = new PropertiesBeanDefinitionReader(reg);
reader.loadBeanDefinitions(new ClassPathResource("bean_config.properties"));
BeanFactory factory = (BeanFactory)reg;
HelloBean helloBean = (HelloBean)factory.getBean("helloBean");
System.out.println(helloBean.getHelloWorld());

InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("ip_config.properties");
Properties p = new Properties();
try {
  p.load(inputStream);
} catch (IOException e1) {
  e1.printStackTrace();
}
System.out.println("ip:"+p.getProperty("ip")+",port:"+p.getProperty("port"));

private WebApplicationContext wac;
wac =WebApplicationContextUtils.getRequiredWebApplicationContext(this.getServletContext());
wac = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());
JdbcTemplate jdbcTemplate = (JdbcTemplate)ctx.getBean("jdbcTemplate");