aspineon · August 27, 2021 09:55 · Jun 2, 2017 · Jun 1, 2017 · May 31, 2017 · May 31, 2017
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -138,3 +138,39 @@ public void doOtherStuff() {
 // PlatformTransactionManager - Interface which is implemented by several Transaction Managers
 // (e.g. JmsTransactionManager, JpaTransactionManager)
 // it has commit() and rollback() as methods
+
+// 3 Steps to achieve transactional behaviour:
+// 1. Set @Transactional on a @Service Bean to achieve that each service method is transactional
+@Service
+@Transactional
+public class MyService {
+  @Autowired
+  private MyRepository myRepo;
+}
+
+// 2. In MyConfig declare a transaction manager
+// 3. Annotate MyConfig with @EnableTransactionManagement
+//    This tells Spring to generate the transactional Proxies
+//    The equivalent in XML configuration is <tx:annotation-driven/>
+@Configuration
+@EnableTransactionManagement
+public class MyConfig {
+  @Bean(name = "transactionManager")
+  @Profile("test")
+  public PlatformTransactionManager transactionManagerForTest() {
+    return new DataSourceTransactionManager(dataSourceForTest());
+  }
+
+  @Bean(name = "dataSource", destroyMethod = "shutdown")
+  @Profile("test")
+  public DataSource dataSourceForTest() {
+    return new EmbeddedDatabaseBuilder()
+      .generateUniqueName(true)
+      .setType(EmbeddedDatabaseType.H2)
+      .setScriptEncoding("UTF-8")
+      .ignoreFailedDrops(true)
+      .addScript("schema.sql")
+      .addScripts("data.sql")
+      .build();
+  }
+}
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -98,4 +98,43 @@ public void myStart() {
   public void myEnd() {
     // do something
   }
-}
+}
+
+// @Transactional - manages a transaction manager
+//
+// Spring doesn't provide any transaction managers itself.
+// It provides hooks to them.
+//
+// Databases have their own transaction managers which will
+// be used by Spring.
+//
+// Spring requests different features of the underlying transaction
+// managers since not all provide the same functionality (e.g. Rollback on Timeout)
+//
+// For @Transactional to work there has to be a Platform Transaction Manager Bean being declared
+// It provides the hook into the underlying transactional system.
+
+// Apply @Transactional to all methods of a class (can be overridden with @Transactional on a specific method)
+@Transactional
+public class MyBean {
+  public void doStuff() {
+  }
+
+  public void doOtherStuff() {
+  }
+}
+
+// Properties of the @Transactional Annotation
+// isolation - enum for isolation levels
+// propagation - enum for propagation levels
+// readOnly - boolean to request a readOnly transaction
+// timeout - integer for a timout period
+// value - String for the name of the transaction manager Bean (Default is: "transactionManager")
+// rollbackFor - List of Exception classes which must trigger a rollback
+// rollbackForClassName - List of Strings with classnames of Exception classes which must trigger a rollback
+// noRollbackFor - List of Exception classes which must not trigger a rollback
+// noRollbackForClassName - List of Strings with classnames of Exception classes which must not trigger a rollback
+
+// PlatformTransactionManager - Interface which is implemented by several Transaction Managers
+// (e.g. JmsTransactionManager, JpaTransactionManager)
+// it has commit() and rollback() as methods
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -71,7 +71,7 @@ public MyBean myBean() {
   }
 }
 
-// Call a method right after the constructor + setter methods and a method after the destruction of a bean
+// Call a method right after the constructor + setter methods and a method before the destruction of a bean
 @Bean(initMethod = "myStart", destroyMethod = "myEnd")
 public MyBean myBean() {
   return new MyBean();

diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -34,6 +34,9 @@ public MyBean myBean() {
 
 bean1 == bean2; // => false
 
+// In a web app (Spring MVC) there are two more Scopes: "request" and "session"
+// It is also possible to define a custom Scope
+
 // Calling a @Bean annotated method multiple times
 // result in the exact same instance of the Bean every time it gets called
 // as the scope is "singleton" by default
@@ -65,4 +68,34 @@ public MyBean myBean() {
       context.add(myBean);
       return myBean;
     }
-  }
+  }
+}
+
+// Call a method right after the constructor + setter methods and a method after the destruction of a bean
+@Bean(initMethod = "myStart", destroyMethod = "myEnd")
+public MyBean myBean() {
+  return new MyBean();
+}
+
+public class MyBean {
+  public void myStart() {
+    // do something
+  }
+
+  public void myEnd() {
+    // do something
+  }
+}
+
+// OR: on the Bean class directly (JSR 330 -> not hardwired to Spring) - Only works with singleton scoped Beans:
+public class MyBean {
+  @PostConstruct
+  public void myStart() {
+    // do something
+  }
+
+  @PreDestroy
+  public void myEnd() {
+    // do something
+  }
+}
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -2,10 +2,10 @@
 @RequestMapping("/users") 
 public @ResponseBody Map<String, String> getUsers () {
 
-    Map<String, String> map = new HashMap<String, String>();
-    map.put("user", "Clark Kent");
+  Map<String, String> map = new HashMap<String, String>();
+  map.put("user", "Clark Kent");
 
-    return map;
+  return map;
 }
 
 // Autowiring multiple Beans of same type into a Java List
@@ -26,10 +26,43 @@
 @Bean
 @Scope("prototype")
 public MyBean myBean() {
-    return new MyBean();
+  return new MyBean();
 }
 
 MyBean bean1 = context.getBean("myBean", MyBean.class);
 MyBean bean2 = context.getBean("myBean", MyBean.class);
 
-bean1 == bean2; // => false
+bean1 == bean2; // => false
+
+// Calling a @Bean annotated method multiple times
+// result in the exact same instance of the Bean every time it gets called
+// as the scope is "singleton" by default
+@Configuration
+public class MyConfig {
+  @Bean
+  public MyBean myBean() {
+    return new MyBean();
+  }
+
+  public void myTestMethod() {
+    MyBean myBean1 = myBean();
+    MyBean myBean2 = myBean();
+
+    myBean1 == myBean2 // => true
+  }
+}
+
+// This is achieved by Spring automatically subclassing the MyConfig Class
+// and overriding the myBean() method somehow like this:
+public class SpringMyConfig extends MyConfig {
+  @Override
+  public MyBean myBean() {
+    if (myBean already in context) {
+      return myBean;
+    }
+    else {
+      MyBean myBean = super.myBean();
+      context.add(myBean);
+      return myBean;
+    }
+  }
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -16,15 +16,20 @@
 ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
 MyBean myFirstBean = context.getBean("myFirstBean", MyBean.class);
 
-// All Spring managed Beans are Singletons
+// By default all Spring managed Beans are Singletons (@Scope("singleton"))
 MyBean bean1 = context.getBean("myBean", MyBean.class);
 MyBean bean2 = context.getBean("myBean", MyBean.class);
 
 bean1 == bean2; // => true
 
-// Create a new Bean on each .getBean(...) call for this type
+// Create a new Bean on each autowiring and each context.getBean() call
 @Bean
 @Scope("prototype")
 public MyBean myBean() {
     return new MyBean();
-}
+}
+
+MyBean bean1 = context.getBean("myBean", MyBean.class);
+MyBean bean2 = context.getBean("myBean", MyBean.class);
+
+bean1 == bean2; // => false
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -14,6 +14,17 @@
 
 // Get a Bean out of the Spring Application Context
 ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
-
 MyBean myFirstBean = context.getBean("myFirstBean", MyBean.class);
 
+// All Spring managed Beans are Singletons
+MyBean bean1 = context.getBean("myBean", MyBean.class);
+MyBean bean2 = context.getBean("myBean", MyBean.class);
+
+bean1 == bean2; // => true
+
+// Create a new Bean on each .getBean(...) call for this type
+@Bean
+@Scope("prototype")
+public MyBean myBean() {
+    return new MyBean();
+}
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -6,4 +6,14 @@
     map.put("user", "Clark Kent");
 
     return map;
-}
+}
+
+// Autowiring multiple Beans of same type into a Java List
+@Autowired
+private List<MyBean> beans;
+
+// Get a Bean out of the Spring Application Context
+ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
+
+MyBean myFirstBean = context.getBean("myFirstBean", MyBean.class);
+
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -6,14 +6,4 @@
     map.put("user", "Clark Kent");
 
     return map;
-}
-
-// Execute Code on Startup (and refresh) of the application
-@Component
-public class MyListener implements ApplicationListener<ContextRefreshedEvent> {
-
-    @Override
-    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
-        // doStuff();
-    }
 }
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -6,4 +6,14 @@
     map.put("user", "Clark Kent");
 
     return map;
+}
+
+// Execute Code on Startup (and refresh) of the application
+@Component
+public class MyListener implements ApplicationListener<ContextRefreshedEvent> {
+
+    @Override
+    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
+        // doStuff();
+    }
 }
diff --git a/spring-cheatsheet.java b/spring-cheatsheet.java
@@ -0,0 +1,9 @@
+// Return JSON without Jackson mapping classes
+@RequestMapping("/users") 
+public @ResponseBody Map<String, String> getUsers () {
+
+    Map<String, String> map = new HashMap<String, String>();
+    map.put("user", "Clark Kent");
+
+    return map;
+}