Differences between getclassloader (). getresourceasstream (filename), Class. getresourceasstream (filename), and (). getcontextclassloader (). getresourceasstream (filename)

I. Preface

When I got the property myself, I met xx. class. getresourceasstream (filename), I don't really understand this. I checked the information online and saw some of the above, So I studied it.

 

Ii. Content

Let's talk about the differences.

Getclassloader (). getresourceasstream ("a.txt"): the path of this method, whether it is an absolute path or a correct path, is obtained from the path, even if ". /a.txt "form to look for, here we need to pay attention to the null pointing to the exception of the situation (you can look at the write here http://cache.baiducontent.com/cm=9d78d513d99c12eb0fb1837e7c4380200e55f0326284915468d5e316ce370d160771e2cb30536713a0b66b6671f30e02b4e47132690c7af1dd8a9f4baea68f7871d57223706bdd124d9b58e5dc46529e778d1bb3f25cf0ba8768d5f18cc4de20089c44040c84f3895803&p=9274c54ad5c246e74bbe9b7c4605bb&ne WP = users & User = Baidu & fm = SC & query = Maven + getclassloader % Ce % aanull & qid = bf473e2d0001b6a7 & p1 = 3 ). Write the bootstrap classloader (start class loader or Bootstrap Class Loader) to load the JDK core APIs. These APIs are generally located under jdk_home/lib. It is a local interface, therefore, it cannot be obtained from Java code. For example, what log (Java. Lang. String. Class. getclassloader () gets is null (reference from the http://blog.csdn.net/benjieming_wang/article/details/5623492 ). Classloader is a type of loader.

Now I will attach the Code Description:

Package Org. wh. properties; import Java. io. ioexception; import Java. io. inputstream; import Java. util. iterator; import Java. util. properties; import Java. util. set; public class propertiesdemo01 {properties prop; Public void setprop (properties prop) {This. prop = prop;} public static void main (string ARGs []) {loadconfig ();} public static properties loadconfig () {properties prop = new properties (); // The getresource () method of the class is from the current. the class file path searches for resources, while the classloader searches for resources from the jar package // inputstream input = properties. class. getresourceasstream ("/jdbcutils. properties "); inputstream input1 = propertiesdemo01.class. getclassloader (). getresourceasstream ("jdbcutils. properties "); system. out. println ("JDK classloader" + properties. class. getclassloader (); // result: JDK Class Loader: NULL system. out. println ("Demo:" + propertiesdemo01.class. getclassloader (); // result: Demo: [email protected] Try {prop. load (input1); @ suppresswarnings ("rawtypes") set keyValue = prop. keyset (); For (iterator A = keyValue. iterator ();. hasnext ();) {string key = (string). next (); string value = prop. getproperty (key); system. out. println ("-key value --" + key + "Value -- Value-" + value) ;}} catch (ioexception e) {e. printstacktrace () ;}return prop ;}}

Conclusion: if the internal JDK class is used here, null pointing to an exception will be reported. We can see that the result of properties. Class. getclassloader () is null;

Class. getresourceasstream (filename): If "/" is added to filename, it indicates the absolute path. Otherwise, it indicates the relative path. The code can be seen above
Thread. currentthread (). getcontextclassloader (): This is the class loader of the current thread,

Package Org. wh. properties; public class test {public static void main (string [] ARGs) {system. out. println (thread. currentthread (). getcontextclassloader (); // The class loader System of the current thread. out. println (test. class. getclassloader (); // The Class Loader of the current class system. out. println (classloader. getsystemclassloader (); // The initial class loader }}

See here for reference: http://stackoverflow.com/questions/676250/different-ways-of-loading-a-file-as-an-inputstream
　　

Differences between getclassloader (). getresourceasstream (filename), Class. getresourceasstream (filename), and (). getcontextclassloader (). getresourceasstream (filename)