Spring配置Bean中注入Enum实例

尝试在spring的配置中的bean中注入Enum，debug跟踪了下spring-context 3.2.5.RELEASE的源码。

最终在类org.springframework.beans.TypeConverterDelegate中的attemptToConvertStringToEnum方法中进行了bean中Enum类型属性的转换。

private Object attemptToConvertStringToEnum(Class<?> requiredType, String trimmedValue, Object currentConvertedValue) {Object convertedValue = currentConvertedValue;if (Enum.class.equals(requiredType)) {// target type is declared as raw enum, treat the trimmed value as <enum.fqn>.FIELD_NAMEint index = trimmedValue.lastIndexOf(".");if (index > - 1) {String enumType = trimmedValue.substring(0, index);String fieldName = trimmedValue.substring(index + 1);ClassLoader loader = this.targetObject.getClass().getClassLoader();try {Class<?> enumValueType = loader.loadClass(enumType);Field enumField = enumValueType.getField(fieldName);convertedValue = enumField.get(null);}catch (ClassNotFoundException ex) {if(logger.isTraceEnabled()) {logger.trace("Enum class [" + enumType + "] cannot be loaded from [" + loader + "]", ex);}}catch (Throwable ex) {if(logger.isTraceEnabled()) {logger.trace("Field [" + fieldName + "] isn't an enum value for type [" + enumType + "]", ex);}}}}if (convertedValue == currentConvertedValue) {// Try field lookup as fallback: for JDK 1.5 enum or custom enum// with values defined as static fields. Resulting value still needs// to be checked, hence we don't return it right away.try {Field enumField = requiredType.getField(trimmedValue);convertedValue = enumField.get(null);}catch (Throwable ex) {if (logger.isTraceEnabled()) {logger.trace("Field [" + convertedValue + "] isn't an enum value", ex);}}}return convertedValue;}

在上面第一个if分支可以看出可在bean中注入Enum实例。在第二个if分支中可以看出能直接注入enum类型的属性。另外从这段代码的处理逻辑，可以看出不仅能注入enum实例，同时可以注入属性类型的静态属性。下面简单的写了个测试

Father.java

package com.jack.test;public class Father {public static final Father INSTANCE = new Father();}

PersonType.java

package com.jack.test;public enum PersonType {STUDENT, TEACHER;}

Sex.java

package com.jack.test;public enum Sex {MALE, FEMALE;}

Person.java

package com.jack.test;public class Person {private Father father;private PersonType type;private Enum<Sex> sex;public Enum<Sex> getSex() {return sex;}public void setSex(Enum<Sex> sex) {this.sex = sex;}public Father getFather() {return father;}public void setFather(Father father) {this.father = father;}public PersonType getType() {return type;}public void setType(PersonType type) {this.type = type;}}

App.java

package com.jack.test;import org.springframework.context.ConfigurableApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import org.springframework.util.Assert;/** * @author jack.L */public class App {public static void main(String[] args) {try (ConfigurableApplicationContext ctx = new ClassPathXmlApplicationContext("context.xml")) {Person person = ctx.getBean(Person.class);Assert.isTrue(person.getFather() == Father.INSTANCE);Assert.isTrue(person.getType() == PersonType.STUDENT);Assert.isTrue(person.getSex() == Sex.MALE);}}}

context.xml

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"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-3.0.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"><bean id="person" class="com.jack.test.Person" p:father="INSTANCE"p:type="STUDENT" p:sex="com.jack.test.Sex.MALE" /></beans>