Spring BeanWrapper分析

最近在读DispatcherServlet 源代码，看到父级类org.springframework.web.servlet.HttpServletBean中关于BeanWrapper的一段代码, 继续追看下去，发现

BeanWrapper 是spring 底层核心的JavaBean包装接口， 默认实现类BeanWrapperImpl.所有bean的属性设置都是通过它来实现。

@Override
    public final void init() throws ServletException {
        if (logger.isDebugEnabled()) {
            logger.debug("Initializing servlet '" + getServletName() + "'");
        }

        // Set bean properties from init parameters.
        try {
            PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
            BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
            ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
            bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
            initBeanWrapper(bw);
            bw.setPropertyValues(pvs, true);
        }
        catch (BeansException ex) {
            logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
            throw ex;
        }

        // Let subclasses do whatever initialization they like.
        initServletBean();

        if (logger.isDebugEnabled()) {
            logger.debug("Servlet '" + getServletName() + "' configured successfully");
        }

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory类 自动注入工厂抽象类

@Override
    public Object configureBean(Object existingBean, String beanName) throws BeansException {
        markBeanAsCreated(beanName);
        BeanDefinition mbd = getMergedBeanDefinition(beanName);
        RootBeanDefinition bd = null;
        if (mbd instanceof RootBeanDefinition) {
            RootBeanDefinition rbd = (RootBeanDefinition) mbd;
            bd = (rbd.isPrototype() ? rbd : rbd.cloneBeanDefinition());
        }
        if (!mbd.isPrototype()) {
            if (bd == null) {
                bd = new RootBeanDefinition(mbd);
            }
            bd.setScope(BeanDefinition.SCOPE_PROTOTYPE);
            bd.allowCaching = false;
        }
       <span style="color:#FF0000;"> BeanWrapper bw = new BeanWrapperImpl(existingBean);</span>
        initBeanWrapper(bw);
        populateBean(beanName, bd, bw);
        return initializeBean(beanName, existingBean, bd);
    }

BeanWrapperImpl 继承了属性编辑注册功能

如何设置值 ：

@Override
    public void setPropertyValue(String propertyName, Object value) throws BeansException {
        BeanWrapperImpl nestedBw;
        try {
           //获取嵌套的属性， like map[my.key]， 没有嵌套属性就返回自己
            nestedBw = getBeanWrapperForPropertyPath(propertyName);
        }
        catch (NotReadablePropertyException ex) {
            throw new NotWritablePropertyException(getRootClass(), this.nestedPath + propertyName,
                    "Nested property in path '" + propertyName + "' does not exist", ex);
        }
        PropertyTokenHolder tokens = getPropertyNameTokens(getFinalPath(nestedBw, propertyName));
        nestedBw.setPropertyValue(tokens, new PropertyValue(propertyName, value));
    }

看下面具体方法的实现

/**
     * Recursively navigate to return a BeanWrapper for the nested property path.
     * @param propertyPath property property path, which may be nested
     * @return a BeanWrapper for the target bean
     */
    protected BeanWrapperImpl getBeanWrapperForPropertyPath(String propertyPath) {
        int pos = PropertyAccessorUtils.getFirstNestedPropertySeparatorIndex(propertyPath);
        // Handle nested properties recursively.
        if (pos > -1) {
            String nestedProperty = propertyPath.substring(0, pos);
            String nestedPath = propertyPath.substring(pos + 1);
                        //递归获取最后一个属性
                        BeanWrapperImpl nestedBw = getNestedBeanWrapper(nestedProperty);
            return nestedBw.getBeanWrapperForPropertyPath(nestedPath);
        }
        else {
            return this;
        }
    }

自己实现了个小例子：

public class HelloWorld {

    private String msg = null;
    private Date date = null;
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
    public Date getDate() {
        return date;
    }
    public void setDate(Date date) {
        this.date = date;
    }

}

package com.sunkey.test;

public class Pepole {

    private String name;

    private int sex;

    private HelloWorld helloWorld;

    public String getName() {
        return name;
    }

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

    public int getSex() {
        return sex;
    }

    public void setSex(int sex) {
        this.sex = sex;
    }

    public HelloWorld getHelloWorld() {
        return helloWorld;
    }

    public void setHelloWorld(HelloWorld helloWorld) {
        this.helloWorld = helloWorld;
    }

}

测试代码：

 @Test
    public void testBeanWapper() throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        Object obj = Class.forName("com.sunkey.test.HelloWorld").newInstance();
        BeanWrapper bw = new BeanWrapperImpl(obj);
        bw.setPropertyValue("msg", "HellowWorld");
        bw.setPropertyValue("date", new Date());
        System.out.println(bw.getPropertyValue("date") + "
" + bw.getPropertyValue("msg"));
    }

    @Test
    public void testNestedBeanWapper() throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        Object obj = Class.forName("com.sunkey.test.HelloWorld").newInstance();
        BeanWrapper bw = new BeanWrapperImpl(obj);
        bw.setPropertyValue("msg", "HellowWorld");
        bw.setPropertyValue("date", new Date());
        Object objP = Class.forName("com.sunkey.test.Pepole").newInstance();
        BeanWrapper pbw = new BeanWrapperImpl(objP);
        pbw.setPropertyValue("name", "jack");
        pbw.setPropertyValue("helloWorld", obj);
        System.out.println(pbw.getPropertyValue("name") + "
" + pbw.getPropertyValue("helloWorld.msg"));
        pbw.setPropertyValue("helloWorld.msg", "HellowWorld修改过");
        System.out.println(pbw.getPropertyValue("name") + "
" + pbw.getPropertyValue("helloWorld.msg")); }