# Spring 自定义属性解析器
- Author: [HuiFer](https://github.com/huifer)
- 源码阅读仓库: [SourceHot-Spring](https://github.com/SourceHot/spring-framework-read)
## 用例
```xml
```
```java
public class DatePropertyRegister implements PropertyEditorRegistrar {
@Override
public void registerCustomEditors(PropertyEditorRegistry registry) {
registry.registerCustomEditor(Date.class, new CustomDateEditor(
new SimpleDateFormat("yyyy-MM-dd"), true)
);
}
}
```
```java
public class DatePropertyEditor extends PropertyEditorSupport {
private String format = "yyyy-MM-dd";
public String getFormat() {
return format;
}
public void setFormat(String format) {
this.format = format;
}
@Override
public void setAsText(String text) throws IllegalArgumentException {
System.out.println(text);
SimpleDateFormat sdf = new SimpleDateFormat(format);
try {
Date date = sdf.parse(text);
this.setValue(date);
} catch (Exception e) {
e.printStackTrace();
}
}
}
```
## PropertyEditorRegistrar解析
- 直接在`DatePropertyRegister`打上断点进行查看注册流程
直接看调用堆栈获取调用层次
```java
@Override
public void registerCustomEditor(Class requiredType, PropertyEditor propertyEditor) {
registerCustomEditor(requiredType, null, propertyEditor);
}
```
```java
@Override
public void registerCustomEditor(@Nullable Class requiredType, @Nullable String propertyPath, PropertyEditor propertyEditor) {
if (requiredType == null && propertyPath == null) {
throw new IllegalArgumentException("Either requiredType or propertyPath is required");
}
if (propertyPath != null) {
if (this.customEditorsForPath == null) {
this.customEditorsForPath = new LinkedHashMap<>(16);
}
this.customEditorsForPath.put(propertyPath, new CustomEditorHolder(propertyEditor, requiredType));
}
else {
if (this.customEditors == null) {
this.customEditors = new LinkedHashMap<>(16);
}
// 放入 customEditors map对象中
this.customEditors.put(requiredType, propertyEditor);
this.customEditorCache = null;
}
}
```
- `PropertyEditorRegistrySupport`
此处对象是通过`DatePropertyRegister`传递的
- `org.springframework.beans.factory.support.AbstractBeanFactory#registerCustomEditors`
```java
protected void registerCustomEditors(PropertyEditorRegistry registry) {
PropertyEditorRegistrySupport registrySupport =
(registry instanceof PropertyEditorRegistrySupport ? (PropertyEditorRegistrySupport) registry : null);
if (registrySupport != null) {
registrySupport.useConfigValueEditors();
}
if (!this.propertyEditorRegistrars.isEmpty()) {
for (PropertyEditorRegistrar registrar : this.propertyEditorRegistrars) {
try {
/**
* {@link ResourceEditorRegistrar#registerCustomEditors(org.springframework.beans.PropertyEditorRegistry)}或者
* {@link PropertyEditorRegistrar#registerCustomEditors(org.springframework.beans.PropertyEditorRegistry)}
*/
registrar.registerCustomEditors(registry);
}
catch (BeanCreationException ex) {
Throwable rootCause = ex.getMostSpecificCause();
if (rootCause instanceof BeanCurrentlyInCreationException) {
BeanCreationException bce = (BeanCreationException) rootCause;
String bceBeanName = bce.getBeanName();
if (bceBeanName != null && isCurrentlyInCreation(bceBeanName)) {
if (logger.isDebugEnabled()) {
logger.debug("PropertyEditorRegistrar [" + registrar.getClass().getName() +
"] failed because it tried to obtain currently created bean '" +
ex.getBeanName() + "': " + ex.getMessage());
}
onSuppressedException(ex);
continue;
}
}
throw ex;
}
}
}
if (!this.customEditors.isEmpty()) {
this.customEditors.forEach((requiredType, editorClass) ->
registry.registerCustomEditor(requiredType, BeanUtils.instantiateClass(editorClass)));
}
}
```
- `void registerCustomEditors(PropertyEditorRegistry registry);` 用例中编写的`DatePropertyRegister`正好有这个方法的实现
·
- 在`AbstractBeanFactory`中查看变量
- 为什么最后结果变成`com.huifer.source.spring.bean.DatePropertyEditor`
看配置文件
```xml
```
- 对应的set方法
```java
public void setCustomEditors(Map, Class> customEditors) {
this.customEditors = customEditors;
}
```
## applyPropertyValues
- 应用属性值
```java
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
if (pvs.isEmpty()) {
return;
}
if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
}
MutablePropertyValues mpvs = null;
// 没有解析的属性
List original;
if (pvs instanceof MutablePropertyValues) {
mpvs = (MutablePropertyValues) pvs;
if (mpvs.isConverted()) {
//MutablePropertyValues 对象中存在转换后对象直接赋值
// Shortcut: use the pre-converted values as-is.
try {
bw.setPropertyValues(mpvs);
return;
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
original = mpvs.getPropertyValueList();
}
else {
original = Arrays.asList(pvs.getPropertyValues());
}
// 自定义转换器
TypeConverter converter = getCustomTypeConverter();
if (converter == null) {
converter = bw;
}
// 创建BeanDefinitionValueResolver
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
// Create a deep copy, resolving any references for values.
// 解析后的对象集合
List deepCopy = new ArrayList<>(original.size());
boolean resolveNecessary = false;
for (PropertyValue pv : original) {
// 解析过的属性
if (pv.isConverted()) {
deepCopy.add(pv);
}
// 没有解析过的属性
else {
// 属性名称
String propertyName = pv.getName();
// 属性值,直接读取到的
Object originalValue = pv.getValue();
// 解析值
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
Object convertedValue = resolvedValue;
/**
* 1. isWritableProperty: 属性可写
* 2. isNestedOrIndexedProperty: 是否循环嵌套
*/
boolean convertible = bw.isWritableProperty(propertyName) &&
!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
if (convertible) {
// 转换器解析
convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
}
// Possibly store converted value in merged bean definition,
// in order to avoid re-conversion for every created bean instance.
if (resolvedValue == originalValue) {
if (convertible) {
// 设置解析值
pv.setConvertedValue(convertedValue);
}
deepCopy.add(pv);
}
// 类型解析
else if (convertible && originalValue instanceof TypedStringValue &&
!((TypedStringValue) originalValue).isDynamic() &&
!(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
pv.setConvertedValue(convertedValue);
deepCopy.add(pv);
}
else {
resolveNecessary = true;
deepCopy.add(new PropertyValue(pv, convertedValue));
}
}
}
if (mpvs != null && !resolveNecessary) {
// 转换成功的标记方法
mpvs.setConverted();
}
// Set our (possibly massaged) deep copy.
try {
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
```
- 属性值解析
```JAVA
@Nullable
private Object convertForProperty(
@Nullable Object value, String propertyName, BeanWrapper bw, TypeConverter converter) {
if (converter instanceof BeanWrapperImpl) {
return ((BeanWrapperImpl) converter).convertForProperty(value, propertyName);
}
else {
PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName);
MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd);
return converter.convertIfNecessary(value, pd.getPropertyType(), methodParam);
}
}
```
```JAVA
private Object doConvertTextValue(@Nullable Object oldValue, String newTextValue, PropertyEditor editor) {
try {
editor.setValue(oldValue);
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug("PropertyEditor [" + editor.getClass().getName() + "] does not support setValue call", ex);
}
// Swallow and proceed.
}
// 调用子类实现方法
editor.setAsText(newTextValue);
return editor.getValue();
}
```
- 调用用例编写的方法
```JAVA
@Override
public void setAsText(String text) throws IllegalArgumentException {
System.out.println(text);
SimpleDateFormat sdf = new SimpleDateFormat(format);
try {
Date date = sdf.parse(text);
this.setValue(date);
} catch (Exception e) {
e.printStackTrace();
}
}
```
该值也是这个方法的返回`org.springframework.beans.TypeConverterDelegate#convertIfNecessary(java.lang.String, java.lang.Object, java.lang.Object, java.lang.Class, org.springframework.core.convert.TypeDescriptor)`