JAVA项目实战-Spring的DI和IOC加载原理
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本节介绍Spring的XML和注解加载Bean,手写简单的源码,仅供参考
/**
* @description: spring的上下文
*
@author
: ZhuCJ
* @date: 2020-08-27 12:32
*/
public
class SpringContext implements BaseFactory{
/**
* 指定扫描的包名
*/private String packerName;
/**
* 指定spring 配置Bean的xml位置
*/private String[] xmlPath;
public SpringContext(String packerName) {
this.packerName = packerName;
}
public SpringContext(String[] xmlPath) {
this.xmlPath = xmlPath;
}
public SpringContext(String packerName, String[] xmlPath) {
this.packerName = packerName;
this.xmlPath = xmlPath;
}
@Override
public Object getBean(String beanName) {
if (Objects.nonNull(this.xmlPath) && xmlPath.length>0){
//加载XML配置Bean loadXml();
}
if (!StringUtils.isEmpty(this.packerName)){
//加载注解配置Bean loadAnnotation();
}
return BEAN_MAP.get(beanName) ;
}
/**
* 创建注解加载工厂
*/publicvoid loadAnnotation(){
new AnnotationBeanFactory(this.packerName);
}
/**
* 创建XML方式工厂
*/publicvoid loadXml(){
for (String xmlPath:this.xmlPath){
new XmlBeanFactory(xmlPath);
}
}
}
/**
* @description:
*
@author
: ZhuCJ
* @date: 2020-08-27 10:16
*/
public
class AnnotationBeanFactory implements BaseFactory {
privatestaticfinal Logger logger = LoggerFactory.getLogger(AnnotationBeanFactory.class);
private String packerName ;
privatestaticfinal String EXT = "class";
@Override
public Object getBean(String beanName) {
return BEAN_MAP.get(beanName);
}
public AnnotationBeanFactory(String packerName){
this.packerName = packerName;
//加载注解Bean loadBean();
//加载注入的属性Bean loadInjectBean();
}
/**
* 加载bean到容器中
*/publicvoid loadBean(){
//读取包名的路径
String packerPath = null;
try {
packerPath = getPkgPath(packerName);
} catch (UnsupportedEncodingException e) {
logger.info("文件路径编码异常:{}",e.getMessage());
thrownew RuntimeException("packerName path error");
}
logger.info("扫描文件目录的路径:{}", packerPath);
// 查找包含Component注解的类
Map<Class<? extends Annotation>, Set<Class<?>>> classesMap = scanClassesByAnnotations(packerName, packerPath, true,
Arrays.asList(ServiceTest.class));
if (classesMap.size() == 0){
logger.error("目录：{}下,未获取到需要加载的类", packerPath);
return;
}
//标记的反射对象
Set<Class<?>> classSet = new HashSet<>();
classesMap.forEach((k, v) -> {
classSet.addAll(v);
});
//默认设置类名为类名小写for (Class<?> classObj:classSet){
Object object = null;
try {
object = classObj.newInstance();
} catch (InstantiationException e) {
thrownew RuntimeException(classObj.getSimpleName()+ " create error");
} catch (IllegalAccessException e) {
thrownew RuntimeException(classObj.getSimpleName()+ " create error");
}
BEAN_MAP.put(StringUtils.uncapitalize(classObj.getSimpleName()),object);
}
}
/**
* 加载注入的Bean属性
*/publicvoid loadInjectBean(){
BEAN_MAP.forEach((k,v)->{
setAttributeValue(v);
});
}
/**
* 根据包名获取包的URL
* @param pkgName com.demo.controller
* @return*/publicstatic String getPkgPath(String pkgName) throws UnsupportedEncodingException {
String pkgDirName = pkgName.replace(‘.‘, File.separatorChar);
URL url = Thread.currentThread().getContextClassLoader().getResource(pkgDirName);
return url == null ? null : URLDecoder.decode(url.getFile(), "UTF-8");
}
/**
* 获取指定包下包含指定注解的所有类对象的集合
* @param pkgName 包名(com.demo.controller)
* @param pkgPath 包路径(/Users/xxx/workspace/java/project/out/production/classes/com/demo/controller)
* @param recursive 是否递归遍历子目录
* @param targetAnnotations 指定注解
* @return 以注解和对应类集合构成的键值对
*/publicstatic Map<Class<? extends Annotation>, Set<Class<?>>> scanClassesByAnnotations(
String pkgName, String pkgPath, finalboolean recursive,
List<Class<? extends Annotation>> targetAnnotations){
Map<Class<? extends Annotation>, Set<Class<?>>> resultMap = new HashMap<>(16);
Collection<File> allClassFile = getAllClassFile(pkgPath, recursive);
for (File curFile : allClassFile){
try {
Class<?> curClass = getClassObj(curFile, pkgPath, pkgName);
for (Class<? extends Annotation> annotation : targetAnnotations){
if (curClass.isAnnotationPresent(annotation)){
if (!resultMap.containsKey(annotation)){
resultMap.put(annotation, new HashSet<Class<?>>());
}
resultMap.get(annotation).add(curClass);
}
}
} catch (ClassNotFoundException e) {
logger.error("load class fail", e);
}
}
return resultMap;
}
/**
* 遍历指定目录下所有扩展名为class的文件
* @param pkgPath 包目录
* @param recursive 是否递归遍历子目录
* @return*/privatestatic Collection<File> getAllClassFile(String pkgPath, boolean recursive){
File fPkgDir = new File(pkgPath);
if (!(fPkgDir.exists() && fPkgDir.isDirectory())){
logger.error("the directory to package is empty: {}", pkgPath);
returnnull;
}
return FileUtils.listFiles(fPkgDir, new String[]{EXT}, recursive);
}
/**
* 加载类
* @param file
* @param pkgPath
* @param pkgName
* @return
* @throws ClassNotFoundException
*/privatestatic Class<?> getClassObj(File file, String pkgPath, String pkgName) throws ClassNotFoundException{
// 考虑class文件在子目录中的情况
String absPath = file.getAbsolutePath().substring(0, file.getAbsolutePath().length() - EXT.length() - 1);
String className = absPath.substring(pkgPath.length()).replace(File.separatorChar, ‘.‘);
className = className.startsWith(".") ? pkgName + className : pkgName + "." + className;
return Thread.currentThread().getContextClassLoader().loadClass(className);
}
/**
* 属性赋值
* @param object
*/privatestaticvoid setAttributeValue(Object object){
Class<?> aClass = object.getClass();
Field[] declaredFields = aClass.getDeclaredFields();
for (Field field:declaredFields){
if (field.isAnnotationPresent(AutowiredTest.class)){
//默认取属性值类型小写为 BeanId
String simpleName = field.getType().getSimpleName();
Object obj = BEAN_MAP.get(StringUtils.uncapitalize(simpleName));
//允许私有属性赋值
field.setAccessible(true);
try {
field.set(object,obj);
} catch (IllegalAccessException e) {
thrownew RuntimeException(field.getName() +" attribute set value exception");
}
}
}
}
publicstaticvoid main(String[] args) {
BaseFactory baseFactory = new AnnotationBeanFactory("com.spring");
BaseFactory baseFactory1 = new XmlBeanFactory("/spring/test.xml");
Body body = (Body) baseFactory.getBean("body");
System.out.println("加载类:"+BaseFactory.BEAN_MAP.size()+"个");
Object apple = baseFactory.getBean("apple");
System.out.println(body);
System.out.println(apple);
Order order = new Order();
for (Field field:order.getClass().getDeclaredFields()){
System.out.println(field.getName());
System.out.println(field.getType().getSimpleName());
}
}
}
/**
* @description: Xml方式创建Bean
*
@author
: ZhuCJ
* @date: 2020-08-26 12:43
*/
public
class XmlBeanFactory implements BaseFactory {
/**
* *******XML形式注册Bean
* 1.指定Resources资源 Xml文件位置
* 2.加载Xml文件Document对象 拿到id 和classes值
* 3.反射创建对象
*/private String filePath;
public XmlBeanFactory(String xmlPath){
this.filePath = xmlPath;
loadBean();
}
@Override
public Object getBean(String beanName) {
return BEAN_MAP.get(beanName);
}
publicvoid loadBean(){
//读取resource资源的路径
String sysPath = ClassUtils.getDefaultClassLoader().getResource("").getPath();
String path = sysPath + filePath;
//dom4j解析XML文件
SAXReader saxReader = new SAXReader();
Document read ;
try {
read = saxReader.read(new File(path));
} catch (Exception e) {
thrownew RuntimeException("file No Find");
}
Element root;
Element rootElement = read.getRootElement();
for (Iterator i = rootElement.elementIterator("bean");i.hasNext();){
root =(Element) i.next();
Attribute id = root.attribute("id");
Attribute aClass = root.attribute("class");
//利用反射创建对象
Class<?> beanClass;
try {
beanClass = Class.forName(aClass.getText());
} catch (ClassNotFoundException e) {
thrownew RuntimeException(id.getText()+"class not Found");
}
Object object = null;
try {
object = beanClass.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
BeanInfo beanInfo = null;
try {
//获取bean对象信息
beanInfo = Introspector.getBeanInfo(beanClass);
} catch (IntrospectionException e) {
e.printStackTrace();
}
//ben对象的属性描述信息
PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
for (Iterator k = root.elementIterator("property");k.hasNext();){
Element propertyElem =(Element) k.next();
Attribute name = propertyElem.attribute("name");
Attribute value = propertyElem.attribute("value");
//判断属性名称,是否和name相等for (PropertyDescriptor desc:propertyDescriptors){
if (desc.getName().equalsIgnoreCase(name.getText())){
Method writeMethod = desc.getWriteMethod();
try {
//赋值 writeMethod.invoke(object,value.getValue());
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
}
}
BEAN_MAP.put(id.getText(),object);
}
}
publicstaticvoid main(String[] args) {
BaseFactory baseFactory = new XmlBeanFactory("/spring/test.xml");
System.out.println(BaseFactory.BEAN_MAP.size());
}
}
/**
* @description: 基础工厂
*
@author
: ZhuCJ
* @date: 2020-08-26 12:42
*/
public
interface
BaseFactory {
/**
静态存放Bean的容器
*/
Map<String,Object> BEAN_MAP = new ConcurrentHashMap();
/**
* 获取bean
* @param beanName
* @return*/
Object getBean(String beanName);
}
/**
* @description: 订单服务
*
@author
: ZhuCJ
* @date: 2020-08-27 13:18
*/
public
interface
OrderService {
/**
* 通过ID查询订单信息
*
@param
id
*
@return
*/
Order selectById (String id);
}
/**
* @description: 订单服务
*
@author
: ZhuCJ
* @date: 2020-08-27 13:18
*/
@ServiceTest
public
class OrderServiceImpl implements OrderService {
@AutowiredTest
private Order order;
@Override
public Order selectById(String id) {
return order;
}
}
/**
* @description: 模拟 spring中属性Autowired注解
*
@author
: ZhuCJ
* @date: 2020-08-27 11:56
*/
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface AutowiredTest {
}
/**
* @description: 模拟spring的标记Service层注解
*
@author
: ZhuCJ
* @date: 2020-08-27 10:17
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface ServiceTest {
}
/**
* @description:
*
@author
: ZhuCJ 80004071
* @date: 2020-08-26 19:09
*/
@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public
class
Order {
private
String id;
private
Date createTime;
private
String orderNo;
}
/**
* @description:
*
@author
: ZhuCJ 80004071
* @date: 2020-08-11 12:36
*/
public
class
Main {
public
static
void
main(String[] args) {
SpringContext springContext = new SpringContext("com.spring",new String[]{"/spring/test.xml"});
OrderService orderServiceImpl =(OrderService) springContext.getBean("orderServiceImpl");
Order order = orderServiceImpl.selectById("1");
System.out.println(order);
}
}
测试结果
我已经被创建
我已经被创建
Order(id=12121212, createTime=null, orderNo=T21000)
加载到容器中Bean数量:10
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原文：https://www.cnblogs.com/zhucj-java/p/13598673.html
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