1 <?xml version="1.0" encoding="UTF-8" ?> 2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3 <html xmlns="http://www.w3.org/1999/xhtml" lang="en"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <link rel="stylesheet" href="resources/doc.css" charset="UTF-8" type="text/css" /> 7 <link rel="shortcut icon" href="resources/report.gif" type="image/gif" /> 8 <title>JaCoCo - FAQ</title> 9 </head> 10 <body> 11 12 <div class="breadcrumb"> 13 <a href="../index.html" class="el_report">JaCoCo</a> > 14 <a href="index.html" class="el_group">Documentation</a> > 15 <span class="el_source">FAQ</span> 16 </div> 17 <div id="content"> 18 19 <h1>FAQ</h1> 20 21 <p> 22 This is a compilation of questions that have been asked by JaCoCo users 23 before. 24 </p> 25 26 <h3>Does JaCoCo have a plug-in for [Eclipse|Netbeans|Whatever...]?</h3> 27 <p> 28 See <a href="integrations.html">this list</a> for current integrations with 29 various tools. 30 </p> 31 32 <h3>What Java versions are supported by JaCoCo?</h3> 33 <p> 34 JaCoCo supports Java class files from version 1.0 to 9. However the minimum 35 JRE version required by the JaCoCo runtime (e.g. the agent) and the JaCoCo 36 tools is 1.5. Also note that class files under test from version 1.6 and above 37 have to contain valid stackmap frames. 38 </p> 39 40 <h3>Why do I get the error "Can't add different class with same name"?</h3> 41 <p> 42 For coverage report generation all classes within a group must have unique 43 names. You get this error during report generation if JaCoCo is supplied with 44 multiple different class files with the same name. To fix this remove those 45 duplicate classes or create separate reports or report groups for each version. 46 </p> 47 48 <h3>Source code lines with exceptions show no coverage. Why?</h3> 49 <p> 50 JaCoCo determines code execution with so called probes. Probes are inserted 51 into the control flow at certain positions. Code is considered as executed 52 when a subsequent probe has been executed. In case of exceptions such a 53 sequence of instructions is aborted somewhere in the middle and the 54 corresponding line of source code is not marked as covered. 55 </p> 56 57 <h3>Why does the coverage report not show line coverage figures?</h3> 58 <p> 59 JaCoCo is based on class files analysis. To calculate line coverage class 60 files must contain line number attributes. For this your code must be compiled 61 with debug information. 62 </p> 63 64 <h3>Why does the coverage report not show highlighted source code?</h3> 65 <p> 66 Make sure the following prerequisites are fulfilled to get source code 67 highlighting in JaCoCo coverage reports: 68 </p> 69 <ul> 70 <li>Class files must be compiled with debug information to contain line numbers.</li> 71 <li>Source files must be properly supplied at report generation time. I.e. 72 specified source folders must be the direct parent of the folders that 73 define the Java packages.</li> 74 </ul> 75 76 <h3>Why does a class show as not covered although it has been executed?</h3> 77 <p> 78 First make sure execution data has been collected. For this select the 79 <i>Sessions</i> link on the top right corner of the HTML report and check 80 whether the class in question is listed. If it is listed but not linked the 81 class at execution time is a different class file. Make sure you're using the 82 exact same class file at runtime as for report generation. Note that some 83 tools (e.g. EJB containers, mocking frameworks) might modify your class files 84 at runtime. Please see the chapter about <a href="classids.html"> class 85 ids</a> for a detailed discussion. 86 </p> 87 88 <h3>Why are Java interface types not shown in the coverage reports?</h3> 89 <p> 90 Java interface methods do not contain code, therefore code coverage cannot 91 be evaluated. Indeed code coverage is recorded for the implementation classes. 92 The same applies to abstract methods in abstract classes. 93 </p> 94 95 <h3>Can I collect coverage information without stopping the JVM?</h3> 96 <p> 97 Yes, there are two possible ways: The JaCoCo <a href="agent.html">agent</a> 98 can be configured for remote control via TCP/IP sockets. This allows to 99 collect execution data at any point in time from a running JVM. The 100 <a href="ant.html#dump"><code>dump</code> Ant task</a> or the 101 <a href="dump-mojo.html"><code>dump</code> Maven goal</a> can be used to 102 request dumps. The remote control feature also allows you to reset execution 103 data. 104 </p> 105 <p> 106 Alternatively the JaCoCo <a href="agent.html">agent</a> can be configured to 107 expose some functionality via JMX (<code>jmx=true</code>). The bean 108 <code><a href="./api/org/jacoco/agent/rt/IAgent.html">org.jacoco:type=Runtime</a></code> 109 provides operations to dump and reset execution data at any point in time. 110 </p> 111 112 <h3>My code uses reflection. Why does it fail when I execute it with JaCoCo?</h3> 113 <p> 114 To collect execution data JaCoCo instruments the classes under test which adds 115 two members to the classes: A private static field <code>$jacocoData</code> 116 and a private static method <code>$jacocoInit()</code>. Both members are 117 marked as synthetic. 118 </p> 119 <p> 120 Please change your code to ignore synthetic members. This is a good practice 121 anyways as also the Java compiler creates synthetic members in certain 122 situation. 123 </p> 124 125 <h3>Why do I get an error while instrumenting certain Java classes?</h3> 126 <p> 127 JaCoCo can instrument valid class files only. Class files with syntactical or 128 semantical error will typically lead to exceptions. In certain areas JaCoCo is 129 more restrictive then the JVM: JaCoCo expects valid so-called "stackmap 130 frame" information in class files of version 1.6 or higher. In turn JaCoCo 131 instrumented classes are expected to conform the specification. 132 </p> 133 <p> 134 Invalid class files are typically created by some frameworks which do not 135 properly adjust stackmap frames when manipulating bytecode. 136 </p> 137 138 <h3>Does JaCoCo run on the IBM JRE J9 and WebSphere?</h3> 139 <p> 140 It does. To make the JaCoCo agent work please set the VM option 141 <code>-Xshareclasses:none</code>. 142 </p> 143 144 <h3>Why do I get a <code>NoClassDefFoundError</code> or 145 <code>ClassNotFoundException</code> for class 146 <code>org.jacoco.agent[...]Offline</code>?</h3> 147 <p> 148 If you use <a href="offline.html">offline instrumentation</a> the instrumented 149 classes get a direct dependency on the JaCoCo runtime. Therefore 150 <code>jacocoagent.jar</code> of the same JaCoCo version must be on the 151 classpath and accessible from by the instrumented classes. 152 </p> 153 154 <h3>Why do I get a <code>StackOverflowError</code> during code coverage analysis?</h3> 155 <p> 156 There are two known reasons for this: 157 </p> 158 <ul> 159 <li>Misconfiguration: If you configure two JaCoCo agents of different releases 160 they will instrument each other and cause a endless recursion. Check the 161 effective java command line and avoid such configurations.</li> 162 <li>Heavy stack usage: JaCoCo instrumentation adds a small runtime overhead 163 by adding a local variable to each method. If your application is already 164 close to the maximum stack size this can eventually lead to an 165 <code>StackOverflowError</code>. Increase the maximum java stack size with 166 the <code>-Xss</code> JVM option.</li> 167 </ul> 168 169 </div> 170 <div class="footer"> 171 <span class="right"><a href="@jacoco.home.url@">JaCoCo</a> @qualified.bundle.version@</span> 172 <a href="license.html">Copyright</a> © @copyright.years@ Mountainminds GmbH & Co. KG and Contributors 173 </div> 174 175 </body> 176 </html> 177
