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tomcat 7 中的类加载器学习

时间:2015-01-26 20:43:28      阅读:183      评论:0      收藏:0      [点我收藏+]

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tomcat 7自带很多junit测试用例,可以帮助我们窥探源码的秘密。以下使用来测试类加载器的一个测试用例。类加载器也是对象,他们用来将类从类从。class文件加载到虚拟机,这些已经讲了很多,深入jvm中说的很详细,什么双亲委派模型,在书中还以tomcat为例讲解。


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package org.apache.catalina.loader;


import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;



import org.junit.Assert;
import org.junit.Test;
import org.apache.catalina.core.StandardContext;
import org.apache.catalina.startup.Tomcat;
import org.apache.catalina.startup.TomcatBaseTest;
import org.apache.tomcat.util.buf.ByteChunk;


public class TestWebappClassLoader extends TomcatBaseTest {


@Test
public void testGetURLs() throws Exception {


File f = new File("test/webresources/war-url-connection.war");


String[] expected = new String[2];
String warUrl = f.toURI().toURL().toExternalForm();
expected[0] = "jar:" + warUrl + "!/WEB-INF/classes/";
expected[1] = "jar:" + warUrl + "!/WEB-INF/lib/test.jar";


Tomcat tomcat = getTomcatInstance();
// Must have a real docBase - just use temp
StandardContext ctx =
(StandardContext)tomcat.addContext("", f.getAbsolutePath());


tomcat.start();


//获得当前的类加载器
ClassLoader cl = ctx.getLoader().getClassLoader();


Assert.assertTrue(cl instanceof URLClassLoader);
//获得类加载器中对应的路径


try (URLClassLoader ucl = (URLClassLoader) cl) {
URL[] urls = ucl.getURLs();
Assert.assertEquals(expected.length, urls.length);
String[] actual = new String[urls.length];
for (int i = 0; i < urls.length; i++) {
actual[i] = urls[i].toExternalForm();
System.out.println(actual[i]);
}
Assert.assertArrayEquals(expected, actual);
//获得类加载器的各级父类加载器
while(cl!=null)
{
System.out.println(cl);
cl=cl.getParent();

}


}
}
@Test
public void testBug53454() throws Exception {
Tomcat tomcat = getTomcatInstance();


// Must have a real docBase - just use temp
StandardContext ctx = (StandardContext)
tomcat.addContext("", System.getProperty("java.io.tmpdir"));
System.out.println("临时目录"+System.getProperty("java.io.tmdir"));


// Map the test Servlet
MyServlet largeBodyServlet = new MyServlet();
Tomcat.addServlet(ctx, "MyServlet", largeBodyServlet);
ctx.addServletMapping("/", "MyServlet");


tomcat.start();


Map<String,List<String>> resHeaders= new HashMap<>();
int rc = headUrl("http://localhost:" + getPort() + "/", new ByteChunk(),
resHeaders);


Assert.assertEquals(HttpServletResponse.SC_OK, rc);
ClassLoader cl=ctx.getClass().getClassLoader();
while(cl!=null)
{
System.out.println(cl);
cl=cl.getParent();
}


}
private static class MyServlet extends HttpServlet {


private static final long serialVersionUID = 1L;


@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {


}

}
}


 

 

输出结果:

临时目录null

sun.misc.Launcher$AppClassLoader@4bb8d481
sun.misc.Launcher$ExtClassLoader@538787fd

jar:file:/F:/javal/Tomcat-Research-trunk/test/webresources/war-url-connection.war!/WEB-INF/classes/
jar:file:/F:/javal/Tomcat-Research-trunk/test/webresources/war-url-connection.war!/WEB-INF/lib/test.jar
WebappClassLoader
  context: 
  delegate: false
----------> Parent Classloader:
sun.misc.Launcher$AppClassLoader@4bb8d481

sun.misc.Launcher$AppClassLoader@4bb8d481
sun.misc.Launcher$ExtClassLoader@538787fd
一月 26, 2015 6:52:56 下午 org.apache.coyote.AbstractProtocol stop
INFO: Stopping ProtocolHandler ["http-nio-127.0.0.1-auto-2-64075"]
一月 26, 2015 6:52:56 下午 org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["http-nio-127.0.0.1-auto-2-64075"]

 

如果使用临时目录和默认目录,应用的类加载器是AppClassLoader,而其的目录可以每个应用的类加载器为WebappClassLoader

 

tomcat 7 中的类加载器学习

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原文地址:http://www.cnblogs.com/hansongjiang/p/4251074.html

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