tomcat 7自帶很多junit測試用例，可以幫助我們窺探源碼的秘密。以下使用來測試類加載器的一個測試用例。類加載器也是對象，他們用來將類從類從。class文件加載到虛擬機，這些已經講了很多，深入jvm中說的很詳細，什么雙親委派模型，在書中還以tomcat為例講解。
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* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
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* http://www.apache.org/licenses/LICENSE-2.0
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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();
//獲得當前的類加載器
ClassLoader cl = ctx.getLoader().getClassLoader();
Assert.assertTrue(cl instanceof URLClassLoader);
//獲得類加載器中對應的路徑
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);
//獲得類加載器的各級父類加載器
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("臨時目錄"+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 {
}
}
}
?
?
輸出結果：
臨時目錄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"]
?
如果使用臨時目錄和默認目錄，應用的類加載器是AppClassLoader,而其的目錄可以每個應用的類加載器為WebappClassLoader
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