Spring源码分析之Resource
基于Spring1.0
public interface InputStreamSource{
InputStream getInputStream() throws IOException;
}
public interface Resource extends InputStreamSource{
boolean exists();
boolean isOpen();
URL getURL() throws IOException;
File getFile() throws IOException;
String getDescription();
}
public abstract class AbstractResource implements Resource{
protected static final String URL_PROTOCOL_FILE = "file";
@Override
public boolean exists(){
try {
return getFile().exists();
}
catch (IOException ex) {
try {
InputStream is = getInputStream();
is.close();
return true;
}
catch (IOException ex2) {
return false;
}
}
}
@Override
public boolean isOpen(){
return false;
}
/**
* 如果实现类重写该方法,则使用子类,如果没有重写,则表示子类不支持该方法,抛出异常
*/
@Override
public URL getURL() throws IOException{
throw new FileNotFoundException(getDescription() + " cannot be resolved to URL");
}
/**
* 如果实现类重写该方法,则使用子类,如果没有重写,则表示子类不支持该方法,抛出异常
*/
@Override
public File getFile() throws IOException{
throw new FileNotFoundException(getDescription() + " cannot be resolved to absolute file path");
}
@Override
public String toString(){
return getDescription();
}
@Override
public boolean equals(Object obj){
return (obj instanceof Resource && ((Resource) obj).getDescription().equals(getDescription()));
}
@Override
public int hashCode(){
return getDescription().hashCode();
}
}
public class ClassPathResource extends AbstractResource{
private final String path;
private Class clazz;
public ClassPathResource(String path){
// /开头表示绝对路径
if (path.startsWith("/")) {
path = path.substring(1);
}
this.path = path;
}
public ClassPathResource(String path, Class clazz){
this.path = path;
this.clazz = clazz;
}
@Override
public InputStream getInputStream() throws IOException{
InputStream is = null;
if (this.clazz != null) {
is = this.clazz.getResourceAsStream(this.path);
} else {
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
is = ccl.getResourceAsStream(this.path);
}
if (is == null) {
throw new FileNotFoundException("Could not open " + getDescription());
}
return is;
}
@Override
public URL getURL() throws IOException{
URL url = null;
if (this.clazz != null) {
url = this.clazz.getResource(this.path);
} else {
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
url = ccl.getResource(this.path);
}
if (url == null) {
throw new FileNotFoundException(getDescription() + " cannot be resolved to URL " +
"because it does not exist");
}
return url;
}
@Override
public File getFile() throws IOException{
URL url = getURL();
if (!URL_PROTOCOL_FILE.equals(url.getProtocol())) {
throw new FileNotFoundException(getDescription() + " cannot be resolved to absolute file path " +
"because it does not reside in the file system: URL=[" + url + "]");
}
return new File(URLDecoder.decode(url.getFile()));
}
@Override
public String getDescription(){
return "class path resource [" + this.path + "]";
}
}
AbstractResource主要实现了两个方法，exists()和 isOpen()， exists方法先通过文件判断资源是否存在，然后根据InputStream进行判断。isOpen()返回false
getURL() ,getFile() 在这里不是抽象方法的原因是因为： 如果实现类重写该方法,则使用子类,如果没有重写,则表示子类不支持该方法,直接抛出异常，避免在实现类中，命名和该方法没关联，还需要抛出异常
比如ClassPathResource重写， InputStreamReSource
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