spring源码学习一

个人的学习总结如下：

1.系统环境变量验证，判断环境是否包含某个变量，如果没有，则启动不了

继承ClassPathXmlApplicationContext，重写initPropertySources方法（由于AbstractApplicationContext的refresh方法中，prepareRefresh中initPropertySources为空，方便后续扩展）

public class MyClassPathXmlApplicationContent extends ClassPathXmlApplicationContext {
public MyClassPathXmlApplicationContent(String configLocations) {
super(configLocations);
}
@Override
protected void initPropertySources() {
System.out.println(this.getEnvironment().getRequiredProperty("abc"));
}
}

2.自定义标签

自定义handler，handler找到parser，parser填充实体

自定义一个实体类

ublic class Jsuper {
private String id;
private String username;
private Integer height;
private Integer age;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Integer getHeight() {
return height;
}
public void setHeight(Integer height) {
this.height = height;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}

　　自定义parser，继承AbstractSingleBeanDefinitionParser,重写getBeanClass，重写doParse方法

public class JsuperBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
@Override
protected Class getBeanClass(Element element) {
return Jsuper.class;
}
@Override
protected void doParse(Element element, BeanDefinitionBuilder builder) {
if(element.hasAttribute("id")){
builder.addPropertyValue("id",element.getAttribute("id"));
}
if(element.hasAttribute("username")){
builder.addPropertyValue("username",element.getAttribute("username"));
}
if(element.hasAttribute("height")){
builder.addPropertyValue("height",element.getAttribute("height"));
}
if(element.hasAttribute("age")){
builder.addPropertyValue("age",element.getAttribute("age"));
}
}
}

　　自定义handler，继承NameSpaceHandlerSupport,重写init方法

public class JsuperNamespaceHandler extends NamespaceHandlerSupport {
@Override
public void init() {
registerBeanDefinitionParser("user",new JsuperBeanDefinitionParser());
}
}

　　resources下新增spring.handlers,spring.schemas

spring.handlers
http\://www.jsuper.com/schema/user=com.jsuper.test.custombean.JsuperNamespaceHandler
spring.schemas
http\://www.jsuper.com/schema/user.xsd=META-INF/user.xsd

View Code

　　新增user.xsd

xml version="1.0" encoding="UTF-8" standalOne="no"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.jsuper.com/schema/user"
xmlns:tns="http://www.jsuper.com/schema/user"
elementFormDefault="qualified">
<element name="user">
<complexType>
<attribute name="id" type="string">attribute>
<attribute name="username" type="string">attribute>
<attribute name="height" type="integer">attribute>
<attribute name="age" type="integer">attribute>
complexType>
element>
schema>

user.xsd

　　在xml中新增

xmlns:jsuper="http://www.jsuper.com/schema/user"
http://www.jsuper.com/schema/user http://www.jsuper.com/schema/user.xsd
<jsuper:user id="aaa" username="zs" age="18" height="180">jsuper:user>

bean.xml

可以从BeanFactory中获取aaa，这里有一个需要注意的，xml中的bean必须有id