Spring记录之模拟IoC(三)

模拟Spring IoC容器 3.0

从xml文件中读取的value值，是String类型，与Java Bean定义的属性，如int,double类型之间如何实现转换呢？

上次说过，Apache Commons BeanUtils包，http://commons.apache.org/proper/commons-beanutils/ 该包集成了许多转化器Converter

用它来实现。

步骤一：加jar包

commons-logging-1.2.jar
commons-beanutils-1.8.3.jar

步骤二：修改容器实现类

修改值注入的地方

package spring.container;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.commons.beanutils.BeanUtils;

import spring.config.Bean;
import spring.config.Property;
import spring.parser.ConfigParser;

/**
* @author Administrator
*
*/
public class Dom4jClassPathXmlApplicationContext implements BeanFactory {

//beans from xml config file
private Map<String, Bean> beans;

// container to store bean
private Map<String, Object> contextMap = new HashMap<String, Object>();

// parse xml file instantly this class is initializing
public Dom4jClassPathXmlApplicationContext(String path) {
beans = ConfigParser.dom4jParser(path);

if (beans != null) {
// loop beans
for (Entry<String, Bean> en : beans.entrySet()) {

String id = en.getKey();
Bean bean = en.getValue();

Object existBean = contextMap.get("id");

// bean is not initialized and scope is singleton
if (existBean == null && bean.getScope().equals("singleton")) {

// initialize bean. 需检验是否已经注入
// Bean must be checked if it is already been initialized
// before this process
Object obj = createBean(bean);

// put beans into the container
contextMap.put(id, obj);
}

}
}
}

/**
* @param bean
* @return
*/
private Object createBean(Bean bean) {

String className = null;

// user reflection
Class clazz = null;
try {
className = bean.getClassName();
clazz = Class.forName(className);
} catch (ClassNotFoundException | NullPointerException e) {
e.printStackTrace();
throw new RuntimeException(className
+ " not found in xml config file.");
}

// generate Objection
Object object = null;
try {
object = clazz.newInstance();
} catch (InstantiationException | IllegalAccessException e) {
e.printStackTrace();
throw new RuntimeException(
"no  default constructor defined in " + className);
}

/**
* <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
*      <property name="driverClassName" value="${jdbc.driverClass}"/>
*      <property name="url" value="${jdbc.url}"/>
* </bean>
*/

// inject property
if (bean.getProperties() != null) {

for (Property properties : bean.getProperties()) {

String propName = null;
Method setterMethod = null;
try {

propName = properties.getName();

// using setter to inject value <property name="name"
// value="changing"/>, <property name="name" ref="ref"/>
setterMethod = BeanMethod.getWriterMethod(object,propName);

} catch (NullPointerException e) {
e.printStackTrace();
throw new RuntimeException("property name is not defined.");
}

// inject value into object using setter
// 这里是值注入，此处通过BeanUtils.populate()方法注入，该方法实现了自动类型转换
if (properties.getValue() != null) {

//use apache BeanUtils tool to inject value so that automation of type change can be done
Map<String, String[]> paraMap = new HashMap<String, String[]>();
paraMap.put(propName, new String[]{properties.getValue()});

try {
BeanUtils.populate(object, paraMap);
} catch (IllegalAccessException | InvocationTargetException e) {
e.printStackTrace();
}

}

// inject another Object
if (properties.getRef() != null) {
// get ref instance
Object refBean = contextMap.get(properties.getRef());

// refBean is not generated. Generate it by recursion
if (refBean == null) {

refBean = createBean(beans.get(properties.getRef()));

if(beans.get(properties.getRef()).getScope().equals("singleton")){
// put refBean into Container if scope in the xml file is singleton
contextMap.put(properties.getRef(), refBean);
}
}

//setter to inject value or ref
try {

setterMethod.invoke(object, refBean);

} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}

}
}

return object;
}

@Override
public Object getBean(String id) {
Object bean = contextMap.get(id);

//if scope is not singleton, then bean does not exist in contextMap and should be null
if(bean == null){
bean = createBean(beans.get(id));
}
return bean;
}

}

步骤三：测试

//在Animal类中增加int类型的age属性，设置getter/setter
<bean id="animal" class="spring.beans.Animal">
<property name="age" value="150"/>
</bean>

@Test
public void testBean(){
Dom4jClassPathXmlApplicationContext context = new Dom4jClassPathXmlApplicationContext("/bean.xml");
Animal animal = (Animal)context.getBean("animal");
System.out.println(animal.getAge());
}

结果