吃透Spring源码：自定义属性编辑器PropertyEditor

Posted 2022-04-09 吃透Java

Spring的强大之处不仅仅在于它为Java开发者提供了极大便利，更在于它的开放式架构，使得用户可以拥有最大扩展Spring的能力。

我们在xml定义bean时，输入的内容都是字符串。spring会根据已经注册好的属性编辑器解析这些字符串，实例化成对应的类型。

一，源码相关

1，创建默认的propertyEditorRegister

在AbstractApplicationContext的refresh()方法的prepareBeanFactory()方法中创建一个默认的PropertyEditorRegister放入beanFactory中，此类主要负责注入如下默认的属性编辑器：

public void registerCustomEditors(PropertyEditorRegistry registry) 
		ResourceEditor baseEditor = new ResourceEditor(this.resourceLoader, this.propertyResolver);
		doRegisterEditor(registry, Resource.class, baseEditor);
		doRegisterEditor(registry, ContextResource.class, baseEditor);
		doRegisterEditor(registry, InputStream.class, new InputStreamEditor(baseEditor));
		doRegisterEditor(registry, InputSource.class, new InputSourceEditor(baseEditor));
		doRegisterEditor(registry, File.class, new FileEditor(baseEditor));
		doRegisterEditor(registry, Path.class, new PathEditor(baseEditor));
		doRegisterEditor(registry, Reader.class, new ReaderEditor(baseEditor));
		doRegisterEditor(registry, URL.class, new URLEditor(baseEditor));

		ClassLoader classLoader = this.resourceLoader.getClassLoader();
		doRegisterEditor(registry, URI.class, new URIEditor(classLoader));
		doRegisterEditor(registry, Class.class, new ClassEditor(classLoader));
		doRegisterEditor(registry, Class[].class, new ClassArrayEditor(classLoader));

		if (this.resourceLoader instanceof ResourcePatternResolver) 
			doRegisterEditor(registry, Resource[].class,
					new ResourceArrayPropertyEditor((ResourcePatternResolver) this.resourceLoader, this.propertyResolver));
		
	

private void doRegisterEditor(PropertyEditorRegistry registry, Class<?> requiredType, PropertyEditor editor) 
		if (registry instanceof PropertyEditorRegistrySupport) 
			((PropertyEditorRegistrySupport) registry).overrideDefaultEditor(requiredType, editor);
		
		else 
			registry.registerCustomEditor(requiredType, editor);
		
	

2，调用registerCustomEditors来完成PropertyEditor的注册

spring源码在实例化bean的时候，创建完BeanWrapperImpl之后会调用registerCustomEditors()方法来遍历所有的propertyEditorRegister（包括我们自定义的propertyEditorRegister）类来完成属性编辑器的注入。如下：

protected void initBeanWrapper(BeanWrapper bw) 
		bw.setConversionService(getConversionService());
		registerCustomEditors(bw);
	

3，调用PropertyEditor来完成属性的解析

在populateBean对属性填充时会遍历每一个属性值来获取对应的属性编辑器，然后调用对应的属性编辑器（PropertyEditor）的setAsText()方法来解析对应的值。

二，案例

Address.java

package com.bobo.customeditor;

/**
 * @author bobo
 * @date 2020-10-21
 */

public class Address 
    private String province;
    private String city;
    private String area;

    public String getProvince() 
        return province;
    

    public void setProvince(String province) 
        this.province = province;
    

    public String getCity() 
        return city;
    

    public void setCity(String city) 
        this.city = city;
    

    public String getArea() 
        return area;
    

    public void setArea(String area) 
        this.area = area;
    

    @Override
    public String toString() 
        return "Address" +
                "province='" + province + '\\'' +
                ", city='" + city + '\\'' +
                ", area='" + area + '\\'' +
                '';
    

Person.java

package com.bobo.customeditor;

/**
 * @author bobo
 * @date 2020-10-21
 */

public class Person 
    private String name;
    private Address address;

    public String getName() 
        return name;
    

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

    public Address getAddress() 
        return address;
    

    public void setAddress(Address address) 
        this.address = address;
    

    @Override
    public String toString() 
        return "Person" +
                "name='" + name + '\\'' +
                ", address=" + address +
                '';
    

AddressPropertyEditor

package com.bobo.customeditor;

import java.beans.PropertyEditorSupport;

/**
 * @author bobo
 * @date 2020-10-21
 */

public class AddressPropertyEdit extends PropertyEditorSupport 
    @Override
    public void setAsText(String text) throws IllegalArgumentException 
        String[] split = text.split("-");
        Address address = new Address();
        address.setProvince(split[0]);
        address.setCity(split[1]);
        address.setArea(split[2]);
        setValue(address);
    

AddressPropertyEditorRegister.java

package com.bobo.customeditor;


import org.springframework.beans.PropertyEditorRegistrar;
import org.springframework.beans.PropertyEditorRegistry;

/**
 * @author bobo
 * @date 2020-10-21
 */

public class AddressPropertyEditorRegister implements PropertyEditorRegistrar 
    @Override
    public void registerCustomEditors(PropertyEditorRegistry registry) 
        registry.registerCustomEditor(Address.class,new AddressPropertyEdit());
    

application-context.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="person" class="com.bobo.customeditor.Person">
        <property name="name" value="bobo"/>
        <property name="address" value="广东省-深圳市-南山区"/>
    </bean>
    <!--第一种方式-->
    <bean class="org.springframework.beans.factory.config.CustomEditorConfigurer">
        <property name="propertyEditorRegistrars">
            <list>
                <bean class="com.bobo.customeditor.AddressPropertyEditorRegister"></bean>
            </list>
        </property>
    </bean>
    <!--第二种方式-->
<!--    <bean class="org.springframework.beans.factory.config.CustomEditorConfigurer">-->
<!--        <property name="customEditors">-->
<!--            <map>-->
<!--                <entry key="com.bobo.customeditor.Address">-->
<!--                    <value>com.bobo.customeditor.AddressPropertyEdit</value>-->
<!--                </entry>-->
<!--            </map>-->
<!--        </property>-->
<!--    </bean>-->
</beans>

test.java

package com.bobo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test 

    public static void main(String[] args) 
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("application-context.xml");
        System.out.println(context.getBean("person"));
    

运行输出：

Personname='bobo', address=Addressprovince='广东省', city='深圳市', area='南山区'