这里我们简单的实现一下spring中的初始化bean，以大概了解他的流程。受委屈几乎是一个人成长最快的途径，吃下去的是委屈，消化掉后得到的是格局。

spring的自定义初始化

测试的项目结构如下：

一、定义两个简单的Bean对象

• FirstBean.java，变量需要set方法：

package com.spring1.bean;

public class FirstBean {
    private String username;
    private String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUserInfo() {
        return username + ", " + password;
    }
}

FirstBean.java

• SecondBean.java，变量需要set方法：

package com.spring1.bean;

public class SecondBean {
    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getUserInfo() {
        return name + ", " + age;
    }
}

SecondBean.java

二、定义一个管理Bean的工厂类BeanFactory

package com.spring1.factory;

import java.util.HashMap;
import java.util.Map;

public class BeanFactory {
    Map<String, Object> map = new HashMap<>();

    public Object getBean(String key) {
        return map.get(key);
    }

    public <T> T getBean(String key, Class<T> tClass) {
        return (T) map.get(key);
    }

    public void setBean(String name, Object object) {
        map.put(name, object);
    }
}

三、定义一个解析xml文件，并把初始化的bean存放到beanFactory的类

package com.spring1.parse;

import com.spring1.SpringUtil;
import com.spring1.factory.BeanFactory;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.List;

public class ParseXmlBean {
    public static BeanFactory parseXmlBean(String filepath) {
        BeanFactory beanFactory = new BeanFactory();
        SAXReader reader = new SAXReader();
        try {
            InputStream stream = ParseXmlBean.class.getClassLoader().getResourceAsStream(filepath);
            Document document = reader.read(stream);
            Element rootElement = document.getRootElement();
            List<Element> entries = rootElement.elements("bean");
            for (Element entry : entries) {
                String beanId = entry.attributeValue("id");
                String beanClass = entry.attributeValue("class");
                Class<?> bean = Class.forName(beanClass);
                Object beanObject = bean.newInstance();
                for (Object subEntry : entry.elements("property")) {
                    String name = ((Element) subEntry).attributeValue("name");
                    String value = ((Element) subEntry).attributeValue("value");
                    String dataType = ((Element) subEntry).attributeValue("dataType");
                    Method method;
                    if (dataType == null) {
                        method = bean.getMethod(getMethodName(name), new Class[]{String.class});
                        method.invoke(beanObject, new Object[]{value});
                    } else if (dataType.equals("int")) {
                        method = bean.getMethod(getMethodName(name), new Class[]{int.class});
                        method.invoke(beanObject, new Object[]{Integer.valueOf(value)});
                    }
                }
                beanFactory.setBean(beanId, beanObject);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return beanFactory;
    }

    private static String getMethodName(String name) {
        return "set" + SpringUtil.firstLetterUpper(name);
    }
}

四、一个简单的工具类

package com.spring1;

public class SpringUtil {
    public static String firstLetterUpper(String name) {
        return name.substring(0, 1).toUpperCase() + name.substring(1);
    }
}

五、测试的主体类如下

package com.spring1.main;

import com.spring1.bean.FirstBean;
import com.spring1.bean.SecondBean;
import com.spring1.factory.BeanFactory;
import com.spring1.parse.ParseXmlBean;
import org.junit.Test;

public class MainTest {
    @Test
    public void test_1() {
        BeanFactory beanFactory = ParseXmlBean.parseXmlBean("config/bean.xml");
        FirstBean firstBean = beanFactory.getBean("firstBean", FirstBean.class);
        String userInfo = firstBean.getUserInfo();
        System.out.println(userInfo);

        SecondBean secondBean = (SecondBean) beanFactory.getBean("secondBean");
        String userInfo1 = secondBean.getUserInfo();
        System.out.println(userInfo1);
    }
}

运行的结果如下：

huhx, 1234
liuling, 21

六、测试的xml文件如下

<beans>
    <bean id="firstBean" class="com.spring1.bean.FirstBean">
        <property name="username" value="huhx"/>
        <property name="password" value="1234"/>
    </bean>

    <bean id="secondBean" class="com.spring1.bean.SecondBean">
        <property name="age" value="21" dataType="int"/>
        <property name="name" value="liuling"/>
    </bean>
</beans>

友情链接