निर्भरता इंजेक्शन में एक विरासत परियोजना का अनुवाद। सीथ का रास्ता

• ऑटो परीक्षणों की एक विकसित प्रणाली का निर्माण
• विभिन्न परियोजनाओं सहित विभिन्न वातावरणों में कोड का पुन: उपयोग
• DI पर निर्मित 3-पक्षीय पुस्तकालयों का उपयोग
• सीखने वाले डीआई

• अधिक जटिल कोड समझ (पहली बार में)
• संदर्भ को कॉन्फ़िगर करने की आवश्यकता है
• सीखने वाले डीआई

कहां से शुरू करें

import org.jetbrains.annotations.Nullable; public class Jedi { private long id; private String name; @Nullable private Long masterId; // fields, constructors, getters/setters, equals, hashCode, toString, etc... public long getId() { return id; } public String getName() { return name; } @Nullable public Long getMasterId() { return masterId; } @Nullable public Jedi getMaster() { if (masterId == null) { return null; } return DBJedi.getJedi(masterId); } } 

 public class DBJedi { public static Jedi getJedi(long id) { DataSource dataSource = ConnectionPools.getDataSource("jedi"); Jedi jedi; // magic return jedi; } } 

 import javax.sql.DataSource; public class DBJedi { private static final DBJedi instance = new DBJedi(); private final ConnectionPools connectionPools; private DBJedi() { this.connectionPools = ConnectionPools.getInstance(); } public static DBJedi getInstance() { return instance; } public Jedi getJedi(long id) { DataSource dataSource = connectionPools.getDataSource("jedi"); Jedi jedi; // magic return jedi; } } 

बुरा अभ्यास 1 - इंजेक्टर के लिए एक स्थिर लिंक रखें

 import org.jetbrains.annotations.NotNull; import org.jetbrains.annotations.TestOnly; import com.google.inject.Injector; // import com.google.common.base.Preconditions; // guava public class InjectorUtil { private static volatile Injector injector; public static void setInjector(@NotNull Injector injector) { // Preconditions.checkNotNull(injector); // Preconditions.checkState(InjectorUtil.injector == null, "Injector already initialized"); InjectorUtil.injector = injector; } @TestOnly public static void rewriteInjector(@NotNull Injector injector) { // Preconditions.checkNotNull(injector); InjectorUtil.injector = injector; } @Deprecated // use fair injection, Sith! @NotNull public static Injector getInjector() { // Preconditions.checkState(InjectorUtil.injector != null, "Injector not initialized"); return InjectorUtil.injector; } } 

 import org.springframework.context.ApplicationContext; import org.springframework.context.ApplicationContextAware; import javax.inject.Named; @Named public class ApplicationContextUtil implements ApplicationContextAware { private static volatile ApplicationContext applicationContext; public void setApplicationContext(ApplicationContext applicationContext) { ApplicationContextUtil.applicationContext = applicationContext; } @Deprecated public static ApplicationContext getApplicationContext() { // Preconditions.checkState(applicationContext != null); return applicationContext; } } 

 @javax.inject.Singleton @javax.inject.Named //   Spring component-scan,  Guice   public class DBJedi { private final ConnectionPools connectionPools; @javax.inject.Inject public DBJedi(ConnectionPools connectionPools) { this.connectionPools = connectionPools; } @Deprecated public static DBJedi getInstance() { return InjectorUtil.getInjector().getInstance(DBJedi.class); } public Jedi getJedi(long id) { DataSource dataSource = connectionPools.getDataSource("jedi"); Jedi jedi; // ... return jedi; } } 

बुरा अभ्यास 2 - बीन फैक्टरी

 public class Jedi { private long id; private String name; @Nullable private Long masterId; private final DBJedi dbJedi; private Jedi(long id, String name, @Nullable masterId, DBJedi dbJedi) { this.id = id; this.name = name; this.masterId = masterId; this.dbJedi = dbJedi; } //... public long getId() { return id; } public String getName() { return name; } @Nullable public Long getMasterId() { return masterId; } @Nullable public Jedi getMaster() { if (masterId == null) { return null; } return dbJedi.getJedi(masterId); } @Singleton @Named public static class Factory { private final DBJedi dbJedi; @Inject public Factory(DBJedi dbJedi) { this.dbJedi = dbJedi; } @Deprecated // refactor Jedi class to simple bean, Sith! public Jedi create(long id, String name, @Nullable masterId) { return new Jedi(id, name, masterId, dbJedi); } } } 

बुरा अभ्यास 3 - परिपत्र निर्भरता

 import javax.inject.Singleton; import javax.inject.Named; import javax.inject.Inject; import javax.inject.Provider; import javax.sql.DataSource; @Singleton @Named public class DBJedi { private final ConnectionPools connectionPools; private final Provider<Jedi.Factory> jediFactoryProvider; @Inject public DBJedi(ConnectionPools connectionPools, Provider<Jedi.Factory> jediFactoryProvider) { this.connectionPools = connectionPools; this.jediFactoryProvider = jediFactoryProvider; } @Deprecated public static DBJedi getInstance() { return InjectorUtil.getInjector().getInstance(DBJedi.class); } public Jedi getJedi(long id) { DataSource dataSource = connectionPools.getDataSource("jedi"); // ... final Jedi.Factory jediFactory = jediFactoryProvider.get(); return jediFactory.create(id, name, masterId); } } 

लेखन परीक्षण

 import org.testng.annotations.*; import com.google.inject.Injector; import com.google.inject.AbstractModule; @Guice(modules = JediTest.JediTestModule.class) public class JediTest { private static final long JEDI_QUI_GON_ID = 12; private static final long JEDI_OBI_WAN_KENOBI_ID = 22; @Inject private Injector injector; @Inject private DBJedi dbJedi; @BeforeClass public void setInjector() { InjectorUtil.rewriteInjector(injector); } @Test public void testJedi() { final Jedi obiWan = dbJedi.getJedi(JEDI_OBI_WAN_KENOBI_ID); final Jedi master = obiWan.getMaster(); Assert.assertEquals(master.getId(), JEDI_QUI_GON_ID); } public static class JediTestModule extends AbstractModule { @Override public void configure() { //  ConnectionPools , ..      bind(ConnectionPools.class).toInstance(new ConnectionPools("pools.properties")); } } } 

परिणाम क्या है?

 public class InjectorUtil { private static final ThreadLocal<Injector> threadLocalInjector = new InheritableThreadLocal<Injector>(); private InjectorUtil() { } /** * Get thread local injector for current thread * * @return * @throws IllegalStateException if not set */ @NotNull public static Injector getInjector() throws IllegalStateException { final Injector Injector = threadLocalInjector.get(); if (Injector == null) { throw new IllegalStateException("Injector not set for current thread"); } return Injector; } /** * Set Injector for current thread * * @param Injector * @throws java.lang.IllegalStateException if already set */ public static void setInjector(@NotNull Injector injector) throws IllegalStateException { if (injector == null) { throw new NullPointerException(); } if (threadLocalInjector.get() != null) { throw new IllegalStateException("Injector already set for current thread"); } threadLocalInjector.set(injector); } /** * Rewrite Injector for current thread, even if already set * * @param injector * @return previous value if was set */ public static Injector rewriteInjector(@NotNull Injector injector) { if (injector == null) { throw new NullPointerException(); } final Injector prevInjector = threadLocalInjector.get(); threadLocalInjector.set(injector); return prevInjector; } /** * Remove Injector from thread local * * @return Injector if was set, else null */ public static Injector removeInjector() { final Injector prevInjector = threadLocalInjector.get(); threadLocalInjector.remove(); return prevInjector; } } 

उन लोगों के लिए जो अंत तक पढ़े हैं