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13  <a href="../index.html" class="el_report">JaCoCo</a> &gt;
14  <a href="index.html" class="el_group">Documentation</a> &gt;
15  <span class="el_source">Java Agent</span>
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18
19<h1>Java Agent</h1>
20
21<p>
22  JaCoCo uses class file instrumentation to record execution coverage data.
23  Class files are instrumented on-the-fly using a so called Java agent. This
24  mechanism allows in-memory pre-processing of all class files during class
25  loading independent of the application framework.
26</p>
27
28<p class="hint">
29  If you use the <a href="ant.html">JaCoCo Ant tasks</a> or
30  <a href="maven.html">JaCoCo Maven plug-in</a> you don't have to care about the
31  agent and its options directly. This is transparently handled by the them.
32</p>
33
34<p>
35  The JaCoCo agent collects execution information and dumps it on request or
36  when the JVM exits. There are three different modes for execution data ouput:
37</p>
38
39<ul>
40  <li>File System: At JVM termination execution data is written to a local
41      file.</li>
42  <li>TCP Socket Server: External tools can connect to the JVM and retrieve
43      execution data over the socket connection. Optional execution data reset
44      and execution data dump on VM exit is possible.</li>
45  <li>TCP Socket Client: At startup the JaCoCo agent connects to a given TCP
46      endpoint. Execution data is written to the socket connection on request.
47      Optional execution data reset and execution data dump on VM exit is
48      possible.</li>
49</ul>
50
51<p>
52  The agent <code>jacocoagent.jar</code> is part of the JaCoCo distribution and
53  includes all required dependencies. A Java agent can be activated with the
54  following JVM option:
55</p>
56
57<pre>
58  -javaagent:<i>[yourpath/]</i>jacocoagent.jar=<i>[option1]</i>=<i>[value1]</i>,<i>[option2]</i>=<i>[value2]</i>
59</pre>
60
61<p>
62  The JaCoCo agent accepts the following options:
63</p>
64
65<table class="coverage">
66  <thead>
67    <tr>
68      <td>Option</td>
69      <td>Description</td>
70      <td>Default</td>
71    </tr>
72  </thead>
73  <tbody>
74    <tr>
75      <td><code>destfile</code></td>
76      <td>Path to the output file for execution data.</td>
77      <td><code>jacoco.exec</code></td>
78    </tr>
79    <tr>
80      <td><code>append</code></td>
81      <td>If set to <code>true</code> and the execution data file already
82          exists, coverage data is appended to the existing file. If set to
83          <code>false</code>, an existing execution data file will be replaced.
84      </td>
85      <td><code>true</code></td>
86    </tr>
87    <tr>
88      <td><code>includes</code></td>
89      <td>A list of class names that should be included in execution analysis.
90          The list entries are separated by a colon (<code>:</code>) and
91          may use wildcard characters (<code>*</code> and <code>?</code>).
92          Except for performance optimization or technical corner cases this
93          option is normally not required.
94      </td>
95      <td><code>*</code> (all classes)</td>
96    </tr>
97    <tr>
98      <td><code>excludes</code></td>
99      <td>A list of class names that should be excluded from execution analysis.
100          The list entries are separated by a colon (<code>:</code>) and
101          may use wildcard characters (<code>*</code> and <code>?</code>).
102          Except for performance optimization or technical corner cases this
103          option is normally not required.
104      </td>
105      <td><i>empty</i> (no excluded classes)</td>
106    </tr>
107    <tr>
108      <td><code>exclclassloader</code></td>
109      <td>A list of class loader names that should be excluded from execution
110          analysis. The list entries are separated by a colon
111          (<code>:</code>) and may use wildcard characters (<code>*</code> and
112          <code>?</code>). This option might be required in case of special
113          frameworks that conflict with JaCoCo code instrumentation, in
114          particular class loaders that do not have access to the Java runtime
115          classes.
116      </td>
117      <td><code>sun.reflect.DelegatingClassLoader</code></td>
118    </tr>
119    <tr>
120      <td><code>inclbootstrapclasses</code></td>
121      <td>Specifies whether also classes from the bootstrap classloader should
122          be instrumented. Use this feature with caution, it needs heavy
123          includes/excludes tuning.
124      </td>
125      <td><code>false</code></td>
126    </tr>
127    <tr>
128      <td><code>sessionid</code></td>
129      <td>A session identifier that is written with the execution data. Without
130          this parameter a random identifier is created by the agent.
131      </td>
132      <td><i>auto-generated</i></td>
133    </tr>
134    <tr>
135      <td><code>dumponexit</code></td>
136      <td>If set to <code>true</code> coverage data will be written on VM
137          shutdown. The dump can only be written if either <code>file</code> is
138          specified or the output is <code>tcpserver</code>/<code>tcpclient</code>
139          and a connection is open at the time when the VM terminates.
140      </td>
141      <td><code>true</code></td>
142    </tr>
143    <tr>
144      <td><code>output</code></td>
145      <td>Output method to use for writing coverage data. Valid options are:
146        <ul>
147          <li><code>file</code>: At VM termination execution data is written to
148              the file specified in the <code>destfile</code> attribute.</li>
149          <li><code>tcpserver</code>: The agent listens for incoming connections
150              on the TCP port specified by the <code>address</code> and
151              <code>port</code> attribute. Execution data is written to this
152              TCP connection.</li>
153          <li><code>tcpclient</code>: At startup the agent connects to the TCP
154              port specified by the <code>address</code> and <code>port</code>
155              attribute. Execution data is written to this TCP connection.</li>
156          <li><code>none</code>: Do not produce any output.</li>
157        </ul>
158        Please see the security considerations below.
159      </td>
160      <td><code>file</code></td>
161    </tr>
162    <tr>
163      <td><code>address</code></td>
164      <td>IP address or hostname to bind to when the output method is
165          <code>tcpserver</code> or connect to when the output method is
166          <code>tcpclient</code>. In <code>tcpserver</code> mode the value
167          "<code>*</code>" causes the agent to accept connections on any local
168          address.
169      </td>
170      <td><i>loopback interface</i></td>
171    </tr>
172    <tr>
173      <td><code>port</code></td>
174      <td>Port to bind to when the output method is <code>tcpserver</code> or
175          connect to when the output method is <code>tcpclient</code>. In
176          <code>tcpserver</code> mode the port must be available, which means
177          that if multiple JaCoCo agents should run on the same machine,
178          different ports have to be specified.
179      </td>
180      <td><code>6300</code></td>
181    </tr>
182    <tr>
183      <td><code>classdumpdir</code></td>
184      <td>Location relative to the working directory where all class files seen
185          by the agent are dumped to. This can be useful for debugging purposes
186          or in case of dynamically created classes for example when scripting
187          engines are used.
188      </td>
189      <td><i>no dumps</i></td>
190    </tr>
191    <tr>
192      <td><code>jmx</code></td>
193      <td>If set to <code>true</code> the agent exposes
194          <a href="./api/org/jacoco/agent/rt/IAgent.html">functionality</a> via
195          JMX under the name <code>org.jacoco:type=Runtime</code>. Please see
196          the security considerations below.
197      </td>
198      <td><code>false</code></td>
199    </tr>
200  </tbody>
201</table>
202
203<h2>Security Consideration for Remote Agent Control</h2>
204
205<p>
206  The ports and connections opened in <code>tcpserver</code> and
207  <code>tcpclient</code> mode and the JMX interface do not provide any
208  authentication mechanism. If you run JaCoCo on production systems make sure
209  that no untrusted sources have access to the TCP server port, or JaCoCo TCP
210  clients only connect to trusted targets. Otherwise internal information of the
211  application might be revealed or DOS attacks are possible.
212</p>
213
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