内容简介：不知何处雨，已觉此间凉。本章我们来实
不知何处雨，已觉此间凉。
概述
本章我们来实 spring 的 setter 注入。 bean-v2.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans>
<bean id = "nioCoder"
class = "com.niocoder.service.v2.NioCoderService">
<property name ="accountDao" ref="accountDao"></property>
<property name ="itemDao" ref="itemDao"></property>
<property name ="url" value="http://niocoder.com/"></property>
</bean>
<bean id="accountDao"
class="com.niocoder.dao.v2.AccountDao">
</bean>
<bean id="itemDao"
class="com.niocoder.dao.v2.ItemDao">
</bean>
</beans>
我们用 BeanDefinition 表达了 <bean> 标签中的 id 和 class 属性，对应的 <property> 标签该如何表达呢？还有 <property> 里面的 ref 和 value ？
新增 PropertyValue 类来表示 property 标签内容，类图如下:
ref 由RuntimeBeanReference表示，value由TypedStringValue表示
增加PropertyValue
PropertyValue
/**
* 描述bean的property属性 如 <property name ="accountDao" ref="accountDao"></property>
* @author zhenglongfei
*/
public class PropertyValue {
/**
* property name ="accountDao"
*/
private final String name;
/**
* property ref="accountDao"
*/
private final Object value;
/**
* 表示是否转换
*/
private Boolean converted = false;
/**
* 转换后的实体类 ref="accountDao" 对应的 new AccountDao();
*/
private Object convertedValue;
public PropertyValue(String name, Object value) {
this.name = name;
this.value = value;
}
public String getName() {
return name;
}
public Object getValue() {
return value;
}
public synchronized boolean isConverted() {
return this.converted;
}
public synchronized Object getConvertedValue() {
return convertedValue;
}
public synchronized void setConvertedValue(Object convertedValue) {
this.convertedValue = convertedValue;
}
}
表示
RuntimeBeanReference
/**
* <property name ="accountDao" ref="accountDao"></property>
* ref="accountDao"
* 表明引用的是bean 获取是会转换成实例
*
* @author zhenglongfei
*/
public class RuntimeBeanReference {
private final String beanName;
public RuntimeBeanReference(String beanName) {
this.beanName = beanName;
}
public String getBeanName() {
return beanName;
}
}
TypedStringValue
/**
* <property name ="url" value="http://niocoder.com/"></property>
* value="http://niocoder.com/"
* 表示 引用的字符串 无需转换
*
* @author zhenglongfei
*/
public class TypedStringValue {
private final String value;
public TypedStringValue(String value) {
this.value = value;
}
public String getValue() {
return value;
}
}
BeanDefinition
public interface BeanDefinition {
......
/**
* 获取bean.xmo 中的 property 标签内容 <property name ="accountDao" ref="accountDao"></property>
* @return
*/
List<PropertyValue> getPropertyValues();
}
> 增加getPropertyValues方法，用于获取property标签
GenericBeanDefinition
public class GenericBeanDefinition implements BeanDefinition {
......
List<PropertyValue> propertyValues = new ArrayList<>();
......
@Override
public List<PropertyValue> getPropertyValues() {
return this.propertyValues;
}
}
实现BeanDefinition
XmlBeanDefinitionReader
@Log
public class XmlBeanDefinitionReader {
......
public void loadBeanDefinition(Resource resource) {
try (InputStream is = resource.getInputStream()) {
SAXReader reader = new SAXReader();
Document doc = reader.read(is);
Element root = doc.getRootElement();
Iterator<Element> elementIterator = root.elementIterator();
while (elementIterator.hasNext()) {
Element ele = elementIterator.next();
String id = ele.attributeValue(ID_ATTRIBUTE);
String beanClassName = ele.attributeValue(CLASS_ATTRIBUTE);
BeanDefinition bd = new GenericBeanDefinition(id, beanClassName);
if (ele.attribute(SCOPE_ATTRIBUTE) != null) {
bd.setScope(ele.attributeValue(SCOPE_ATTRIBUTE));
}
// 解析property标签
parsePropertyElement(ele, bd);
this.registry.registerBeanDefinition(id, bd);
}
} catch (Exception e) {
throw new BeanDefinitionStoreException("IOException parsing XML document", e);
}
}
private void parsePropertyElement(Element ele, BeanDefinition bd) {
Iterator iterator = ele.elementIterator(PROPERTY_ELEMENT);
while (iterator.hasNext()) {
Element propElem = (Element) iterator.next();
String propertyName = propElem.attributeValue(NAME_ATTRIBUTE);
if (!StringUtils.hasLength(propertyName)) {
log.info("Tag 'property' must have a 'name' attribute");
return;
}
Object val = parsePropertyValue(propElem, bd, propertyName);
PropertyValue pv = new PropertyValue(propertyName, val);
bd.getPropertyValues().add(pv);
}
}
private Object parsePropertyValue(Element propElem, BeanDefinition bd, String propertyName) {
String elementName = (propertyName != null) ?
"<property> element for property '" + propertyName + "'" :
"<constructor-arg> element";
boolean hasRefAttribute = (propElem.attribute(REF_ATTRIBUTE) != null);
boolean hasValueAttribute = (propElem.attribute(VALUE_ATTRIBUTE) != null);
if (hasRefAttribute) {
String refName = propElem.attributeValue(REF_ATTRIBUTE);
if (!StringUtils.hasText(refName)) {
log.info(elementName + " contains empty 'ref' attribute");
}
// 表示是ref =""
RuntimeBeanReference ref = new RuntimeBeanReference(refName);
return ref;
} else if (hasValueAttribute) {
// 表示名value=""
TypedStringValue valueHolder = new TypedStringValue(propElem.attributeValue(VALUE_ATTRIBUTE));
return valueHolder;
} else {
throw new RuntimeException(elementName + " must specify a ref or value");
}
}
}
解析property标签，区分ref属性和value属性
BeanDefinitionTestV2
@Log
public class XmlBeanDefinitionReader {
......
public void loadBeanDefinition(Resource resource) {
try (InputStream is = resource.getInputStream()) {
SAXReader reader = new SAXReader();
Document doc = reader.read(is);
Element root = doc.getRootElement();
Iterator<Element> elementIterator = root.elementIterator();
while (elementIterator.hasNext()) {
Element ele = elementIterator.next();
String id = ele.attributeValue(ID_ATTRIBUTE);
String beanClassName = ele.attributeValue(CLASS_ATTRIBUTE);
BeanDefinition bd = new GenericBeanDefinition(id, beanClassName);
if (ele.attribute(SCOPE_ATTRIBUTE) != null) {
bd.setScope(ele.attributeValue(SCOPE_ATTRIBUTE));
}
// 解析property标签
parsePropertyElement(ele, bd);
this.registry.registerBeanDefinition(id, bd);
}
} catch (Exception e) {
throw new BeanDefinitionStoreException("IOException parsing XML document", e);
}
}
private void parsePropertyElement(Element ele, BeanDefinition bd) {
Iterator iterator = ele.elementIterator(PROPERTY_ELEMENT);
while (iterator.hasNext()) {
Element propElem = (Element) iterator.next();
String propertyName = propElem.attributeValue(NAME_ATTRIBUTE);
if (!StringUtils.hasLength(propertyName)) {
log.info("Tag 'property' must have a 'name' attribute");
return;
}
Object val = parsePropertyValue(propElem, bd, propertyName);
PropertyValue pv = new PropertyValue(propertyName, val);
bd.getPropertyValues().add(pv);
}
}
private Object parsePropertyValue(Element propElem, BeanDefinition bd, String propertyName) {
String elementName = (propertyName != null) ?
"<property> element for property '" + propertyName + "'" :
"<constructor-arg> element";
boolean hasRefAttribute = (propElem.attribute(REF_ATTRIBUTE) != null);
boolean hasValueAttribute = (propElem.attribute(VALUE_ATTRIBUTE) != null);
if (hasRefAttribute) {
String refName = propElem.attributeValue(REF_ATTRIBUTE);
if (!StringUtils.hasText(refName)) {
log.info(elementName + " contains empty 'ref' attribute");
}
// 表示是ref =""
RuntimeBeanReference ref = new RuntimeBeanReference(refName);
return ref;
} else if (hasValueAttribute) {
// 表示名value=""
TypedStringValue valueHolder = new TypedStringValue(propElem.attributeValue(VALUE_ATTRIBUTE));
return valueHolder;
} else {
throw new RuntimeException(elementName + " must specify a ref or value");
}
}
}
测试是否能解析 property标签
代码下载
BeanDefinitionValueResolver
虽然我们已经使用 PropertyValue 来表达 property 标签，并且也可以区分是 ref 和 value 属性，但并没有真正的获取 ref 对应 bean 的实例。
BeanDefinitionValueResolver
/**
* 将<property name ="accountDao" ref="accountDao"></property>
* accountDao 转换成实例bean
*
* @author zhenglongfei
*/
public class BeanDefinitionValueResolver {
// 含factory 因为factory有getBean方法
private final DefaultBeanFactory factory;
public BeanDefinitionValueResolver(DefaultBeanFactory factory) {
this.factory = factory;
}
public Object resolveValueIfNecessary(Object value) {
// 判断是ref 还是value
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
String refName = ref.getBeanName();
Object bean = this.factory.getBean(refName);
return bean;
} else if (value instanceof TypedStringValue) {
return ((TypedStringValue) value).getValue();
} else {
// TODO
throw new RuntimeException("the value " + value + " has not implemented");
}
}
}
根据property标签的ref和value返回对应的实例或字符串
DefaultBeanFactory
public class DefaultBeanFactory extends DefaultSingletonBeanRegistry implements BeanFactory, BeanDefinitionRegistry {
......
private Object createBean(BeanDefinition bd) {
// 1. 创建实例
Object bean = instantiateBean(bd);
// 2. 设置属性
populateBean(bd, bean);
return bean;
}
private void populateBean(BeanDefinition bd, Object bean) {
List<PropertyValue> pvs = bd.getPropertyValues();
if (pvs == null || pvs.isEmpty()) {
return;
}
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this);
try {
for (PropertyValue pv : pvs) {
String propertyName = pv.getName();
Object originalValue = pv.getValue();
Object resolvedValue = valueResolver.resolveValueIfNecessary(originalValue);
pv.setConvertedValue(resolvedValue);
// set 注入 使用java BeanInfo 实现
BeanInfo beanInfo = Introspector.getBeanInfo(bean.getClass());
PropertyDescriptor[] pds = beanInfo.getPropertyDescriptors();
for (PropertyDescriptor pd : pds) {
if (pd.getName().equals(propertyName)) {
pd.getWriteMethod().invoke(bean, resolvedValue);
break;
}
}
}
} catch (Exception ex) {
throw new BeanCreationException("Failed to obtain BeanInfo for class [" + bd.getBeanClassName() + "]", ex);
}
}
private Object instantiateBean(BeanDefinition bd) {
ClassLoader cl = ClassUtils.getDefaultClassLoader();
String beanClassName = bd.getBeanClassName();
try {
Class<?> clz = cl.loadClass(beanClassName);
// 使用反射创建bean的实例，需要对象存在默认的无参构造方法
return clz.newInstance();
} catch (Exception e) {
throw new BeanCreationException("create bean for " + beanClassName + " failed", e);
}
}
}
创建完bean的实例之后使用java BeanInfo设置属性值
BeanDefinitionValueResolverTest2
public class BeanDefinitionValueResolverTest2 {
DefaultBeanFactory factory = null;
XmlBeanDefinitionReader reader = null;
BeanDefinitionValueResolver resolver = null;
@Before
public void setUp() {
factory = new DefaultBeanFactory();
reader = new XmlBeanDefinitionReader(factory);
reader.loadBeanDefinition(new ClassPathResource("bean-v2.xml"));
resolver = new BeanDefinitionValueResolver(factory);
}
@Test
public void testResolveRuntimeBeanReference() {
RuntimeBeanReference reference = new RuntimeBeanReference("accountDao");
Object value = resolver.resolveValueIfNecessary(reference);
Assert.assertNotNull(value);
Assert.assertTrue(value instanceof AccountDao);
}
@Test
public void testResolveTypedStringValue() {
TypedStringValue stringValue = new TypedStringValue("http://niocoder.com/");
Object value = resolver.resolveValueIfNecessary(stringValue);
Assert.assertNotNull(value);
Assert.assertEquals("http://niocoder.com/", value);
}
}
测试BeanDefinitionValueResolver
ApplicationContextTestV2
public class ApplicationContextTestV2 {
@Test
public void testGetBeanProperty() {
ApplicationContext ctx = new ClassPathXmlApplicationContext("bean-v2.xml");
NioCoderService nioCoderService = (NioCoderService) ctx.getBean("nioCoder");
Assert.assertNotNull(nioCoderService.getAccountDao());
Assert.assertNotNull(nioCoderService.getItemDao());
Assert.assertNotNull(nioCoderService.getUrl());
assertTrue(nioCoderService.getItemDao() instanceof ItemDao);
assertTrue(nioCoderService.getAccountDao() instanceof AccountDao);
assertEquals(nioCoderService.getUrl(), "http://niocoder.com/");
}
}
测试setter 注入
代码下载
PropertyEditorSupport
如果你在 NioCoderService 中新增一个 Integer 类型的属性，你会发现上面的 setter 注入失败,这是为什么呢？
因为不管属性是任何类型（double,float,Integer等）在配置文件中都是对应的字符串类型的字面值,如果想要实现类型转换则需要使用 java.beans.PropertyEditor 的编辑器。
CustomNumberEditor
public class CustomNumberEditor extends PropertyEditorSupport {
private final Class<? extends Number> numberClass;
private final NumberFormat numberFormat;
private final boolean allowEmpty;
public CustomNumberEditor(Class<? extends Number> numberClass, boolean allowEmpty) throws IllegalArgumentException {
this(numberClass, null, allowEmpty);
}
public CustomNumberEditor(Class<? extends Number> numberClass,
NumberFormat numberFormat, boolean allowEmpty) throws IllegalArgumentException {
if (numberClass == null || !Number.class.isAssignableFrom(numberClass)) {
throw new IllegalArgumentException("Property class must be a subclass of Number");
}
this.numberClass = numberClass;
this.numberFormat = numberFormat;
this.allowEmpty = allowEmpty;
}
@Override
public void setAsText(String text) throws IllegalArgumentException {
if (this.allowEmpty && !StringUtils.hasText(text)) {
// Treat empty String as null value.
setValue(null);
} else if (this.numberFormat != null) {
// Use given NumberFormat for parsing text.
setValue(NumberUtils.parseNumber(text, this.numberClass, this.numberFormat));
} else {
// Use default valueOf methods for parsing text.
setValue(NumberUtils.parseNumber(text, this.numberClass));
}
}
@Override
public String getAsText() {
Object value = getValue();
if (value == null) {
return "";
}
if (this.numberFormat != null) {
// Use NumberFormat for rendering value.
return this.numberFormat.format(value);
} else {
// Use toString method for rendering value.
return value.toString();
}
}
}
Integer 类型转换器
CustomNumberEditorTest
public class CustomNumberEditorTest {
@Test
public void testConvertString2Number() {
CustomNumberEditor editor = new CustomNumberEditor(Integer.class, true);
editor.setAsText("1");
Object value = editor.getValue();
Assert.assertTrue(value instanceof Integer);
Assert.assertEquals(1, ((Integer) editor.getValue()).intValue());
editor.setAsText("");
Assert.assertTrue(editor.getValue() == null);
try {
editor.setAsText("3.1");
} catch (IllegalArgumentException e) {
return;
}
Assert.fail();
}
}
测试类
代码下载
封装类型转换器
虽然已经实现了类型转换，但对应的每种基础类型都需要转换一下，因此我们封装一个类型转换款的方法。类图如下
TypeConverter
/**
* 封装类型转换的接口
*
* @author zhenglongfei
* @see CustomBooleanEditor
* @see CustomDateEditor
* @see CustomNumberEditor
*/
public interface TypeConverter {
/**
* 用于类型转换
*
* @param value bean.xml中value或者ref
* @param requiredType 需要转换的类型
* @param <T>
* @return
* @throws TypeMismatchException
*/
<T> T convertIfNecessary(Object value, Class<T> requiredType) throws TypeMismatchException;
}
封装类型转换器接口
SimpleTypeConverter
/**
* TypeConverter 实现类
*
* @author zhenglongfei
*/
public class SimpleTypeConverter implements TypeConverter {
private Map<Class<?>, PropertyEditor> defaultEditors;
public SimpleTypeConverter() {
}
@Override
public <T> T convertIfNecessary(Object value, Class<T> requiredType) throws TypeMismatchException {
// 如果requiredType是对象或者字符串 直接返回
if (ClassUtils.isAssignableValue(requiredType, value)) {
return (T) value;
} else {
// 根据传入的requiredType选择对应的editor
if (value instanceof String) {
PropertyEditor editor = findDefaultEditor(requiredType);
try {
editor.setAsText((String) value);
} catch (IllegalArgumentException e) {
throw new TypeMismatchException(value, requiredType);
}
return (T) editor.getValue();
} else {
throw new RuntimeException("Todo : can't convert value for " + value + " class:" + requiredType);
}
}
}
private PropertyEditor findDefaultEditor(Class<?> requiredType) {
PropertyEditor editor = this.getDefaultEditor(requiredType);
if (editor == null) {
throw new RuntimeException("Editor for " + requiredType + " has not been implemented");
}
return editor;
}
public PropertyEditor getDefaultEditor(Class<?> requiredType) {
if (this.defaultEditors == null) {
createDefaultEditors();
}
return this.defaultEditors.get(requiredType);
}
private void createDefaultEditors() {
this.defaultEditors = new HashMap<Class<?>, PropertyEditor>(64);
// Spring's CustomBooleanEditor accepts more flag values than the JDK's default editor.
this.defaultEditors.put(boolean.class, new CustomBooleanEditor(false));
this.defaultEditors.put(Boolean.class, new CustomBooleanEditor(true));
this.defaultEditors.put(Date.class, new CustomDateEditor(true));
this.defaultEditors.put(int.class, new CustomNumberEditor(Integer.class, false));
this.defaultEditors.put(Integer.class, new CustomNumberEditor(Integer.class, true));
}
}
实现类
bean-v2.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans>
<bean id="nioCoder"
class="com.niocoder.service.v2.NioCoderService">
<property name="accountDao" ref="accountDao"></property>
<property name="itemDao" ref="itemDao"></property>
<property name="url" value="http://niocoder.com/"></property>
<property name="birthday" value="2019-01-21"></property>
<property name="flag" value="true"></property>
<property name="version" value="1"></property>
</bean>
<bean id="accountDao"
class="com.niocoder.dao.v2.AccountDao">
</bean>
<bean id="itemDao"
class="com.niocoder.dao.v2.ItemDao">
</bean>
</beans>
增加 date类型birthday boolean类型flag Integer类型version
DefaultBeanFactory
public class DefaultBeanFactory extends DefaultSingletonBeanRegistry implements BeanFactory, BeanDefinitionRegistry {
...
private void populateBean(BeanDefinition bd, Object bean) {
List<PropertyValue> pvs = bd.getPropertyValues();
if (pvs == null || pvs.isEmpty()) {
return;
}
// 处理 bean.xml 中的 ref 和 value 对应 RuntimeBeanReference TypedStringValue
// <property name="itemDao" ref="itemDao"></property>
// <property name="url" value="http://niocoder.com/"></property>
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this);
// 处理bean.xml中的特殊类型 Integer Boolean Date 等
// <property name="birthday" value="2019-01-21"></property>
// <property name="flag" value="true"></property>
// <property name="version" value="1"></property>
SimpleTypeConverter converter = new SimpleTypeConverter();
try {
for (PropertyValue pv : pvs) {
String propertyName = pv.getName();
Object originalValue = pv.getValue();
Object resolvedValue = valueResolver.resolveValueIfNecessary(originalValue);
pv.setConvertedValue(resolvedValue);
pv.setConverted(true);
// set 注入 使用java BeanInfo 实现
BeanInfo beanInfo = Introspector.getBeanInfo(bean.getClass());
PropertyDescriptor[] pds = beanInfo.getPropertyDescriptors();
for (PropertyDescriptor pd : pds) {
if (pd.getName().equals(propertyName)) {
// 类型转换
Object convertedValue = converter.convertIfNecessary(resolvedValue, pd.getPropertyType());
pd.getWriteMethod().invoke(bean, convertedValue);
break;
}
}
}
} catch (Exception ex) {
throw new BeanCreationException("Failed to obtain BeanInfo for class [" + bd.getBeanClassName() + "]", ex);
}
}
....
}
类型转换
TypeConverterTest
public class TypeConverterTest {
@Test
public void testConvertStringToObject() {
TypeConverter converter = new SimpleTypeConverter();
// Integer
{
Integer integer = converter.convertIfNecessary("1", Integer.class);
Assert.assertEquals(1, integer.intValue());
try {
converter.convertIfNecessary("3.1", Integer.class);
} catch (TypeMismatchException e) {
return;
}
fail();
}
// boolean
{
Boolean b = converter.convertIfNecessary("true", Boolean.class);
Assert.assertEquals(b, b.booleanValue());
try {
converter.convertIfNecessary("xxxxxxxx", Integer.class);
} catch (TypeMismatchException e) {
return;
}
fail();
}
// date
{
Date birthday = converter.convertIfNecessary("2019-01-22", Date.class);
Assert.assertTrue(birthday instanceof Date);
try {
converter.convertIfNecessary("20190122", Date.class);
} catch (TypeMismatchException e) {
return;
}
fail();
}
// AccountDao
{
AccountDao accountDao = converter.convertIfNecessary(new AccountDao(), AccountDao.class);
Assert.assertNotNull(accountDao);
}
}
}
ApplicationContextTestV2
public class ApplicationContextTestV2 {
@Test
public void testGetBeanProperty() {
ApplicationContext ctx = new ClassPathXmlApplicationContext("bean-v2.xml");
NioCoderService nioCoderService = (NioCoderService) ctx.getBean("nioCoder");
Assert.assertNotNull(nioCoderService.getAccountDao());
Assert.assertNotNull(nioCoderService.getItemDao());
Assert.assertNotNull(nioCoderService.getUrl());
Assert.assertNotNull(nioCoderService.getBirthday());
Assert.assertNotNull(nioCoderService.getFlag());
Assert.assertNotNull(nioCoderService.getVersion());
assertTrue(nioCoderService.getItemDao() instanceof ItemDao);
assertTrue(nioCoderService.getAccountDao() instanceof AccountDao);
assertEquals(nioCoderService.getUrl(), "http://niocoder.com/");
assertTrue(nioCoderService.getBirthday() instanceof Date);
assertTrue(nioCoderService.getFlag());
assertEquals(nioCoderService.getVersion(), new Integer(1));
}
}
校验
代码下载
代码下载
参考资料
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