1 package org.junit.rules; 2 3 import org.junit.runner.Description; 4 import org.junit.runners.model.Statement; 5 6 /** 7 * A base class for Rules (like TemporaryFolder) that set up an external 8 * resource before a test (a file, socket, server, database connection, etc.), 9 * and guarantee to tear it down afterward: 10 * 11 * <pre> 12 * public static class UsesExternalResource { 13 * Server myServer= new Server(); 14 * 15 * @Rule 16 * public ExternalResource resource= new ExternalResource() { 17 * @Override 18 * protected void before() throws Throwable { 19 * myServer.connect(); 20 * }; 21 * 22 * @Override 23 * protected void after() { 24 * myServer.disconnect(); 25 * }; 26 * }; 27 * 28 * @Test 29 * public void testFoo() { 30 * new Client().run(myServer); 31 * } 32 * } 33 * </pre> 34 */ 35 public abstract class ExternalResource implements TestRule { apply(Statement base, Description description)36 public Statement apply(Statement base, Description description) { 37 return statement(base); 38 } 39 statement(final Statement base)40 private Statement statement(final Statement base) { 41 return new Statement() { 42 @Override 43 public void evaluate() throws Throwable { 44 before(); 45 try { 46 base.evaluate(); 47 } finally { 48 after(); 49 } 50 } 51 }; 52 } 53 54 /** 55 * Override to set up your specific external resource. 56 * @throws if setup fails (which will disable {@code after} 57 */ 58 protected void before() throws Throwable { 59 // do nothing 60 } 61 62 /** 63 * Override to tear down your specific external resource. 64 */ 65 protected void after() { 66 // do nothing 67 } 68 } 69