解决循环引用导致的StackOverflow，json配置String强转等问题

pom.xml

@@ -15,6 +15,19 @@
                     <target>1.8</target>
                 </configuration>
             </plugin>
+            <plugin>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <configuration>
+                    <archive>
+                        <manifest>
+                            <mainClass>com.allen.capturewebdata.Main</mainClass>
+                        </manifest>
+                    </archive>
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
     <packaging>jar</packaging>
@@ -33,16 +46,20 @@
             <version>4.12</version>
             <scope>test</scope>
         </dependency>
+
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-api</artifactId>
             <version>1.7.22</version>
+            <scope>provided</scope>
         </dependency>
         <dependency>
             <groupId>ch.qos.logback</groupId>
             <artifactId>logback-classic</artifactId>
             <version>1.1.8</version>
+            <scope>provided</scope>
         </dependency>
+
         <dependency>
             <groupId>org.reflections</groupId>
             <artifactId>reflections</artifactId>

src/main/java/bean/BeanContainer.java

@@ -4,6 +4,7 @@
 import bean.annotation.Init;
 import bean.annotation.Value;
 import bean.converter.*;
+import bean.exception.CircularReferenceException;
 import conf.Source;
 import org.apache.commons.lang3.StringUtils;
 import org.reflections.ReflectionUtils;
@@ -152,18 +153,44 @@ public <T> T get(Class<T> beanClass) {
                     candidates.add(entry.getValue());
                 }
             }
-            int size = candidates.size();
-            if (size > 1) {
-                throw new IllegalStateException("Given bean class has one more candidates: " + getCandidatesInfo(candidates) + ".");
-            }
-            if (size == 1) {
-                BeanWrapper beanWrapper = candidates.get(0);
+            BeanWrapper beanWrapper = findEligibleCandidate(candidates, beanClass);
+            if (beanWrapper != null) {
                 result = (T) loadBean(beanWrapper);
             }
         }
         return result;
     }
 
+    /**
+     * 在候选者中寻找最合适的一个，逻辑:
+     * <ul>
+     * <li>如果candidates为空，那么直接返回null.</li>
+     * <li>如果candidates大小为1，那么返回第一个.</li>
+     * <li>如果candidates大小大于1，那么寻找targetClass与requiredType相等(==)的候选者.</li>
+     * </ul>
+     *
+     * @throws IllegalStateException 如果发现多个候选者
+     */
+    private <T> BeanWrapper findEligibleCandidate(List<BeanWrapper> candidates, Class<T> requiredType) {
+        int size = candidates.size();
+        BeanWrapper result = null;
+        if (size == 1) {
+            result = candidates.get(0);
+        } else if (size > 1) {
+            for (int i = 0; i < size; i++) {
+                if (candidates.get(i).getTargetClass() == requiredType) {
+                    result = candidates.get(i);
+                    break;
+                }
+            }
+            if (result == null) {
+                throw new IllegalStateException("Given bean class has one more candidates: " +
+                        getCandidatesInfo(candidates) + ".");
+            }
+        }
+        return result;
+    }
+
     /**
      * 获得所有clazz类型的bean.
      *
@@ -190,14 +217,28 @@ public <T> List<T> getBeansWithType(Class<T> clazz) {
      *
      * @param beanWrapper {@linkplain BeanWrapper} 非空
      * @return 初始化的bean实例
+     * @throws CircularReferenceException 如果满足以下条件:
+     *                                    <ul>
+     *                                    <li>{@link #allowCircularReference}设为false.</li>
+     *                                    <li>bean尚未完成初始化(构造器).</li>
+     *                                    <li>bean的{@link Scope}不为{@linkplain Scope#SINGLETOM}.</li>
+     *                                    </ul>
      */
     private Object loadBean(BeanWrapper beanWrapper) {
         Object result = beanWrapper.getTarget();
+        if (beanWrapper.isCurrentlyInCreation()) {
+            if (!allowCircularReference || (result == null) || beanWrapper.getScope() != Scope.SINGLETOM) {
+                throw new CircularReferenceException("Circular reference bean '" + beanWrapper.getBeanName() + "'.");
+            }
+            return result;
+        }
         if (result == null || beanWrapper.getScope() == Scope.PROTOTYPE) {
-            result = createBean(beanWrapper.getTargetClass());
+            beanWrapper.setCurrentlyInCreation(true);
+            result = createBean(beanWrapper);
             if (result != null && beanWrapper.getScope() == Scope.SINGLETOM) {
                 beanWrapper.setTarget(result);
             }
+            beanWrapper.setCurrentlyInCreation(false);
         }
         return result;
     }
@@ -214,9 +255,14 @@ private String getCandidatesInfo(List<BeanWrapper> candidates) {
     /**
      * 创建bean实例.
      */
-    private Object createBean(Class beanClass) {
+    private Object createBean(BeanWrapper beanWrapper) {
+        Class beanClass = beanWrapper.getTargetClass();
         Object instance = newInstance(beanClass);
         if (instance != null) {
+            if (allowCircularReference && beanWrapper.getScope() == Scope.SINGLETOM) {
+                //earlyReference
+                beanWrapper.setTarget(instance);
+            }
             if (source != null) {
                 injectConfs(instance, beanClass);
             }
@@ -285,17 +331,22 @@ private Object[] resolveArgs(Parameter[] parameters) {
      */
     private Object resolveArg(Parameter parameter) {
         Value value = parameter.getAnnotation(Value.class);
-        Object result;
+        Object result = null;
+        //jdk1.8 javac -parameters参数
+        String name = (parameter.isNamePresent() ? parameter.getName() : null);
         if (value != null) {
-            //jdk1.8 javac -parameters参数
-            String name = (parameter.isNamePresent() ? parameter.getName() : null);
             result = resolveConfByValue(parameter, name, parameter.getType(), parameter.getParameterizedType());
         } else {
             Class type = parameter.getType();
             if (type.isPrimitive()) {
                 throw new IllegalStateException("Can't inject to primitive type: " + parameter + ".");
             }
-            result = get(type);
+            if (name != null) {
+                result = get(name);
+            }
+            if (result == null) {
+                result = get(type);
+            }
         }
         return result;
     }

src/main/java/bean/BeanWrapper.java

@@ -17,7 +17,6 @@ public class BeanWrapper {
      * 是否正在创建对应的bean实例.
      */
     private boolean currentlyInCreation = false;
-    //TODO 被构造器依赖?
 
     public Scope getScope() {
         return scope;
@@ -51,13 +50,22 @@ public void setTarget(Object target) {
         this.target = target;
     }
 
+    public boolean isCurrentlyInCreation() {
+        return currentlyInCreation;
+    }
+
+    public void setCurrentlyInCreation(boolean currentlyInCreation) {
+        this.currentlyInCreation = currentlyInCreation;
+    }
+
     @Override
     public String toString() {
         return "BeanWrapper{" +
                 "scope=" + scope +
                 ", beanName='" + beanName + '\'' +
                 ", targetClass=" + targetClass +
                 ", target=" + target +
+                ", currentlyInCreation=" + currentlyInCreation +
                 '}';
     }
 

src/main/java/bean/exception/CircularReferenceException.java

@@ -0,0 +1,14 @@
+package bean.exception;
+
+/**
+ * 循环引用.
+ *
+ * @author skywalker
+ */
+public class CircularReferenceException extends RuntimeException {
+
+    public CircularReferenceException(String message) {
+        super(message);
+    }
+
+}

src/main/java/conf/JsonSource.java

@@ -54,7 +54,7 @@ private String readAsString() throws IOException {
 
     @Override
     public String get(String key) {
-        return (String) doGet(key);
+        return doGet(key).toString();
     }
 
     private Object doGet(String key) {

src/test/java/ioc/IOCTest.java

@@ -32,7 +32,7 @@ public void getByName() throws LoadException {
         Injecter injecter = new Injecter().source(source);
         BeanContainer container = injecter.basePackage("ioc").inject();
         Teacher teacher = (Teacher) container.get("teacher");
-        teacher.printStudent();
+        System.out.println(teacher);
     }
 
     /**
@@ -43,18 +43,7 @@ public void getByNameNull() {
         Injecter injecter = new Injecter();
         BeanContainer container = injecter.basePackage("ioc").inject();
         Teacher teacher = (Teacher) container.get("tea");
-        teacher.printStudent();
-    }
-
-    /**
-     * 测试bean name冲突的情况.需要将{@link Student}的名改为teacher.
-     */
-    @Test(expected = IllegalStateException.class)
-    public void nameComplict() {
-        Injecter injecter = new Injecter();
-        BeanContainer container = injecter.basePackage("ioc").inject();
-        Teacher teacher = (Teacher) container.get("teacher");
-        teacher.printStudent();
+        System.out.println(teacher.toString());
     }
 
     /**
@@ -81,9 +70,9 @@ public void threadSafe() throws ExecutionException, InterruptedException {
         Injecter injecter = new Injecter();
         BeanContainer container = injecter.basePackage("ioc").inject();
         ExecutorService service = Executors.newFixedThreadPool(2);
-        Callable<Student> task = () -> container.get(Student.class);
-        Future<Student> s1 = service.submit(task);
-        Future<Student> s2 = service.submit(task);
+        Callable<Teacher> task = () -> container.get(Teacher.class);
+        Future<Teacher> s1 = service.submit(task);
+        Future<Teacher> s2 = service.submit(task);
         service.shutdown();
         Assert.assertTrue(s1.get() == s2.get());
     }
@@ -96,10 +85,9 @@ public void getWithType() throws LoadException {
         CompositeSource source = new CompositeSource();
         source.registerSource(new JsonSource("etc/conf.json"), new PropertiesSource("etc/db.properties"),
                 new XmlSource("etc/test.xml"));
-        Injecter injecter = new Injecter().source(source);
+        Injecter injecter = new Injecter().source(source).allowCircularReference(true);
         BeanContainer container = injecter.basePackage("ioc").inject();
-        List<Student> students = container.getBeansWithType(Student.class);
-        System.out.println(students);
+        System.out.println(container.get(Student.class));
     }
 
 }

src/test/java/ioc/Student.java

@@ -1,13 +1,17 @@
 package ioc;
 
+import bean.Scope;
+import bean.annotation.Component;
+
 import javax.annotation.Resource;
 
 /**
  * 学生.
  *
  * @author skywalker
  */
-public abstract class Student {
+@Component(scope = Scope.PROTOTYPE)
+public class Student {
 
     @Resource
     private Teacher teacher;

src/test/java/ioc/Teacher.java

@@ -12,15 +12,6 @@
 @Component
 public class Teacher implements BeanContainerAware {
 
-    private Student student;
-
-    public Teacher(Student student) {
-        this.student = student;
-    }
-
-    public void printStudent() {
-        System.out.println(student);
-    }
 
     @Override
     public void setBeanContainer(BeanContainer beanContainer) {

src/test/java/json/JsonTest.java

@@ -19,7 +19,7 @@ public class JsonTest {
     public void test() throws LoadException {
         Source source = new JsonSource("etc/conf.json");
         Injecter injecter = new Injecter();
-        BeanContainer beanContainer = injecter.basePackage("xml").source(source).inject();
+        BeanContainer beanContainer = injecter.basePackage("json").source(source).inject();
         JsonHolder holder = beanContainer.get(JsonHolder.class);
         System.out.println(holder);
     }