Java程序在默认情况下是没有安装默认的安全管理器， 所以如果需要使用安全管理器， 需要在运行时指定启动项：-Djava.security.manager。
但在使用JUnit运行时，比如运行测试用例，可能会出现问题：
java.security.AccessControlException: access denied (java.net.SocketPermission 127.0.0.1:3063 connect,resolve)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkConnect(SecurityManager.java:1034)
at java.net.Socket.connect(Socket.java:513)
at java.net.Socket.connect(Socket.java:469)
at java.net.Socket.<init>(Socket.java:366)
at java.net.Socket.<init>(Socket.java:180)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.connect(RemoteTestRunner.java:570)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:373)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
看如下程序：
public class SecurityManager1Test {
/**
* -Djava.security.manager
*
* permission java.net.SocketPermission "127.0.0.1:*", "connect,resolve";
* permission java.lang.RuntimePermission "accessDeclaredMembers";
*/
@Test
public void getSecurityManager() {
SecurityManager sm = System.getSecurityManager();
if (sm == null) {
System.out.println("no security manager");
} else {
System.out.println("exist security manager");
}
}
}
在运行时如果不加上启动项：-Djava.security.manager，运行结果如下：
no security manager
如果加上启动项：-Djava.security.manager，运行结果如下：
java.security.AccessControlException: access denied (java.net.SocketPermission 127.0.0.1:3070 connect,resolve)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkConnect(SecurityManager.java:1034)
at java.net.Socket.connect(Socket.java:513)
at java.net.Socket.connect(Socket.java:469)
at java.net.Socket.<init>(Socket.java:366)
at java.net.Socket.<init>(Socket.java:180)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.connect(RemoteTestRunner.java:570)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:373)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
这个时候需要添加访问权限，具体在jre\lib\security\java.policy策略文件中添加访问策略。
在上面的错误信息， 应该是没有java.net.SocketPermission 127.0.0.1:3165 connect,resolve访问权限，打开jre\lib\security\java.policy， 在最后添加：
permission java.net.SocketPermission "127.0.0.1:*", "connect,resolve";
运行后结果如下：
java.security.AccessControlException: access denied (java.lang.RuntimePermission accessDeclaredMembers)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkMemberAccess(SecurityManager.java:1662)
at java.lang.Class.checkMemberAccess(Class.java:2157)
at java.lang.Class.getDeclaredMethods(Class.java:1790)
at org.junit.internal.MethodSorter.getDeclaredMethods(MethodSorter.java:54)
at org.junit.runners.model.TestClass.scanAnnotatedMembers(TestClass.java:65)
at org.junit.runners.model.TestClass.<init>(TestClass.java:57)
at org.junit.runners.ParentRunner.createTestClass(ParentRunner.java:88)
at org.junit.runners.ParentRunner.<init>(ParentRunner.java:83)
at org.junit.runners.BlockJUnit4ClassRunner.<init>(BlockJUnit4ClassRunner.java:65)
at org.junit.internal.builders.JUnit4Builder.runnerForClass(JUnit4Builder.java:10)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:33)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.createUnfilteredTest(JUnit4TestLoader.java:84)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.createTest(JUnit4TestLoader.java:70)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.loadTests(JUnit4TestLoader.java:43)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:444)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
还是报错，需要添加java.lang.RuntimePermission accessDeclaredMembers访问策略，打开jre\lib\security\java.policy， 在最后添加：
permission java.lang.RuntimePermission "accessDeclaredMembers";
运行后结果如下：
exist security manager