jacoco/org.jacoco.doc/docroot/doc/faq.html - toolchain/jack - Git at Google

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   <title>JaCoCo - FAQ</title>
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 <div class="breadcrumb">
   <a href="../index.html" class="el_report">JaCoCo</a> &gt;
   <a href="index.html" class="el_group">Documentation</a> &gt;
   <span class="el_source">FAQ</span>
 </div>
 <div id="content">

 <h1>FAQ</h1>

 <p>
   This is a compilation of questions that have been asked by JaCoCo users
   before.
 </p>

 <h3>Does JaCoCo have a plug-in for [Eclipse|Netbeans|Whatever...]?</h3>
 <p>
   See <a href="integrations.html">this list</a> for current integrations with
   various tools.
 </p>

 <h3>What Java versions are supported by JaCoCo?</h3>
 <p>
   JaCoCo supports Java class files from version 1.0 to 1.8. However the minimum
   JRE version required by the JaCoCo runtime (e.g. the agent) and the JaCoCo
   tools is 1.5. Also note that class files under test from version 1.6 and above
   have to contain valid stackmap frames.
 </p>

 <h3>Why do I get the error "Can't add different class with same name"?</h3>
 <p>
   For coverage report generation all classes within a group must have unique
   names. You get this error during report generation if JaCoCo is supplied with
   multiple different class files with the same name. To fix this remove those
   duplicate classes or create separate reports or report groups for each version.
 </p>

 <h3>Source code lines with exceptions show no coverage. Why?</h3>
 <p>
   JaCoCo determines code execution with so called probes. Probes are inserted
   into the control flow at certain positions. Code is considered as executed
   when a subsequent probe has been executed. In case of exceptions such a
   sequence of instructions is aborted somewhere in the middle and the
   corresponding line of source code is not marked as covered.
 </p>

 <h3>Why does the coverage report not show line coverage figures?</h3>
 <p>
   JaCoCo is based on class files analysis. To calculate line coverage class
   files must contain line number attributes. For this your code must be compiled
   with debug information.
 </p>

 <h3>Why does the coverage report not show highlighted source code?</h3>
 <p>
   Make sure the following prerequisites are fulfilled to get source code
   highlighting in JaCoCo coverage reports:
 </p>
 <ul>
   <li>Class files must be compiled with debug information to contain line numbers.</li>
   <li>Source files must be properly supplied at report generation time. I.e.
       specified source folders must be the direct parent of the folders that
       define the Java packages.</li>
 </ul>

 <h3>Why does a class show as not covered although it has been executed?</h3>
 <p>
   First make sure execution data has been collected. For this select the
   <i>Sessions</i> link on the top right corner of the HTML report and check
   whether the class in question is listed. If it is listed but not linked the
   class at execution time is a different class file. Make sure you're using the
   exact same class file at runtime as for report generation. Note that some
   tools (e.g. EJB containers, mocking frameworks) might modify your class files
   at runtime. Please see the chapter about <a href="classids.html"> class
   ids</a> for a detailed discussion.
 </p>

 <h3>Why are Java interface types not shown in the coverage reports?</h3>
 <p>
   Java interface methods do not contain code, therefore code coverage cannot
   be evaluated. Indeed code coverage is recorded for the implementation classes.
   The same applies to abstract methods in abstract classes.
 </p>

 <h3>Can I collect coverage information without stopping the JVM?</h3>
 <p>
   Yes, there are two possible ways: The JaCoCo <a href="agent.html">agent</a>
   can be configured for remote control via TCP/IP sockets. This allows to
   collect execution data at any point in time from a running JVM. The
   <a href="ant.html#dump"><code>dump</code> Ant task</a> or the
   <a href="dump-mojo.html"><code>dump</code> Maven goal</a> can be used to
   request dumps. The remote control feature also allows you to reset execution
   data.
 </p>
 <p>
   Alternatively the JaCoCo <a href="agent.html">agent</a> can be configured to
   expose some functionality via JMX (<code>jmx=true</code>). The bean
   <code><a href="./api/org/jacoco/agent/rt/IAgent.html">org.jacoco:type=Runtime</a></code>
   provides operations to dump and reset execution data at any point in time.
 </p>

 <h3>My code uses reflection. Why does it fail when I execute it with JaCoCo?</h3>
 <p>
   To collect execution data JaCoCo instruments the classes under test which adds
   two members to the classes: A private static field <code>$jacocoData</code>
   and a private static method <code>$jacocoInit()</code>. Both members are
   marked as synthetic.
 </p>
 <p>
   Please change your code to ignore synthetic members. This is a good practice
   anyways as also the Java compiler creates synthetic members in certain
   situation.
 </p>

 <h3>Why do I get an error while instrumenting certain Java classes?</h3>
 <p>
   JaCoCo can instrument valid class files only. Class files with syntactical or
   semantical error will typically lead to exceptions. In certain areas JaCoCo is
   more restrictive then the JVM: JaCoCo expects valid so-called "stackmap
   frame" information in class files of version 1.6 or higher. In turn JaCoCo
   instrumented classes are expected to conform the specification.
 </p>
 <p>
   Invalid class files are typically created by some frameworks which do not
   properly adjust stackmap frames when manipulating bytecode.
 </p>

 <h3>Does JaCoCo run on the IBM JRE J9 and WebSphere?</h3>
 <p>
   It does. To make the JaCoCo agent work please set the VM option
   <code>-Xshareclasses:none</code>.
 </p>

 </div>
 <div class="footer">
   <span class="right"><a href="@jacoco.home.url@">JaCoCo</a> @qualified.bundle.version@</span>
   <a href="license.html">Copyright</a> &copy; @copyright.years@ Mountainminds GmbH &amp; Co. KG and Contributors
 </div>

 </body>
 </html>
	<?xml version="1.0" encoding="UTF-8" ?>
	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml" lang="en">
	<head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
	<link rel="stylesheet" href=".resources/doc.css" charset="UTF-8" type="text/css" />
	<link rel="shortcut icon" href=".resources/report.gif" type="image/gif" />
	<title>JaCoCo - FAQ</title>
	</head>
	<body>

	<div class="breadcrumb">
	<a href="../index.html" class="el_report">JaCoCo</a> >
	<a href="index.html" class="el_group">Documentation</a> >
	<span class="el_source">FAQ</span>
	</div>
	<div id="content">

	<h1>FAQ</h1>

	<p>
	This is a compilation of questions that have been asked by JaCoCo users
	before.
	</p>

	<h3>Does JaCoCo have a plug-in for [Eclipse\|Netbeans\|Whatever...]?</h3>
	<p>
	See <a href="integrations.html">this list</a> for current integrations with
	various tools.
	</p>

	<h3>What Java versions are supported by JaCoCo?</h3>
	<p>
	JaCoCo supports Java class files from version 1.0 to 1.8. However the minimum
	JRE version required by the JaCoCo runtime (e.g. the agent) and the JaCoCo
	tools is 1.5. Also note that class files under test from version 1.6 and above
	have to contain valid stackmap frames.
	</p>

	<h3>Why do I get the error "Can't add different class with same name"?</h3>
	<p>
	For coverage report generation all classes within a group must have unique
	names. You get this error during report generation if JaCoCo is supplied with
	multiple different class files with the same name. To fix this remove those
	duplicate classes or create separate reports or report groups for each version.
	</p>

	<h3>Source code lines with exceptions show no coverage. Why?</h3>
	<p>
	JaCoCo determines code execution with so called probes. Probes are inserted
	into the control flow at certain positions. Code is considered as executed
	when a subsequent probe has been executed. In case of exceptions such a
	sequence of instructions is aborted somewhere in the middle and the
	corresponding line of source code is not marked as covered.
	</p>

	<h3>Why does the coverage report not show line coverage figures?</h3>
	<p>
	JaCoCo is based on class files analysis. To calculate line coverage class
	files must contain line number attributes. For this your code must be compiled
	with debug information.
	</p>

	<h3>Why does the coverage report not show highlighted source code?</h3>
	<p>
	Make sure the following prerequisites are fulfilled to get source code
	highlighting in JaCoCo coverage reports:
	</p>
	<ul>
	<li>Class files must be compiled with debug information to contain line numbers.</li>
	<li>Source files must be properly supplied at report generation time. I.e.
	specified source folders must be the direct parent of the folders that
	define the Java packages.</li>
	</ul>

	<h3>Why does a class show as not covered although it has been executed?</h3>
	<p>
	First make sure execution data has been collected. For this select the
	<i>Sessions</i> link on the top right corner of the HTML report and check
	whether the class in question is listed. If it is listed but not linked the
	class at execution time is a different class file. Make sure you're using the
	exact same class file at runtime as for report generation. Note that some
	tools (e.g. EJB containers, mocking frameworks) might modify your class files
	at runtime. Please see the chapter about <a href="classids.html"> class
	ids</a> for a detailed discussion.
	</p>

	<h3>Why are Java interface types not shown in the coverage reports?</h3>
	<p>
	Java interface methods do not contain code, therefore code coverage cannot
	be evaluated. Indeed code coverage is recorded for the implementation classes.
	The same applies to abstract methods in abstract classes.
	</p>

	<h3>Can I collect coverage information without stopping the JVM?</h3>
	<p>
	Yes, there are two possible ways: The JaCoCo <a href="agent.html">agent</a>
	can be configured for remote control via TCP/IP sockets. This allows to
	collect execution data at any point in time from a running JVM. The
	<a href="ant.html#dump"><code>dump</code> Ant task</a> or the
	<a href="dump-mojo.html"><code>dump</code> Maven goal</a> can be used to
	request dumps. The remote control feature also allows you to reset execution
	data.
	</p>
	<p>
	Alternatively the JaCoCo <a href="agent.html">agent</a> can be configured to
	expose some functionality via JMX (<code>jmx=true</code>). The bean
	<code><a href="./api/org/jacoco/agent/rt/IAgent.html">org.jacoco:type=Runtime</a></code>
	provides operations to dump and reset execution data at any point in time.
	</p>

	<h3>My code uses reflection. Why does it fail when I execute it with JaCoCo?</h3>
	<p>
	To collect execution data JaCoCo instruments the classes under test which adds
	two members to the classes: A private static field <code>$jacocoData</code>
	and a private static method <code>$jacocoInit()</code>. Both members are
	marked as synthetic.
	</p>
	<p>
	Please change your code to ignore synthetic members. This is a good practice
	anyways as also the Java compiler creates synthetic members in certain
	situation.
	</p>

	<h3>Why do I get an error while instrumenting certain Java classes?</h3>
	<p>
	JaCoCo can instrument valid class files only. Class files with syntactical or
	semantical error will typically lead to exceptions. In certain areas JaCoCo is
	more restrictive then the JVM: JaCoCo expects valid so-called "stackmap
	frame" information in class files of version 1.6 or higher. In turn JaCoCo
	instrumented classes are expected to conform the specification.
	</p>
	<p>
	Invalid class files are typically created by some frameworks which do not
	properly adjust stackmap frames when manipulating bytecode.
	</p>

	<h3>Does JaCoCo run on the IBM JRE J9 and WebSphere?</h3>
	<p>
	It does. To make the JaCoCo agent work please set the VM option
	<code>-Xshareclasses:none</code>.
	</p>

	</div>
	<div class="footer">
	<span class="right"><a href="@jacoco.home.url@">JaCoCo</a> @qualified.bundle.version@</span>
	<a href="license.html">Copyright</a> © @copyright.years@ Mountainminds GmbH & Co. KG and Contributors
	</div>

	</body>
	</html>