Example usage for org.springframework.beans.factory.support AutowireUtils sortConstructors

Introduction

In this page you can find the example usage for org.springframework.beans.factory.support AutowireUtils sortConstructors.

Prototype

public static void sortConstructors(Constructor<?>[] constructors) 

Source Link

Document

Sort the given constructors, preferring public constructors and "greedy" ones with a maximum number of arguments.

Usage

From source file:org.springframework.beans.factory.support.ConstructorResolver.java

/**
 * "autowire constructor" (with constructor arguments by type) behavior.
 * Also applied if explicit constructor argument values are specified,
 * matching all remaining arguments with beans from the bean factory.
 * <p>This corresponds to constructor injection: In this mode, a Spring
 * bean factory is able to host components that expect constructor-based
 * dependency resolution./*from ww  w  . j a  v  a2  s .  co m*/
 * @param beanName the name of the bean
 * @param mbd the merged bean definition for the bean
 * @param chosenCtors chosen candidate constructors (or {@code null} if none)
 * @param explicitArgs argument values passed in programmatically via the getBean method,
 * or {@code null} if none (-> use constructor argument values from bean definition)
 * @return a BeanWrapper for the new instance
 */
public BeanWrapper autowireConstructor(final String beanName, final RootBeanDefinition mbd,
        @Nullable Constructor<?>[] chosenCtors, @Nullable final Object[] explicitArgs) {

    BeanWrapperImpl bw = new BeanWrapperImpl();
    this.beanFactory.initBeanWrapper(bw);

    Constructor<?> constructorToUse = null;
    ArgumentsHolder argsHolderToUse = null;
    Object[] argsToUse = null;

    if (explicitArgs != null) {
        argsToUse = explicitArgs;
    } else {
        Object[] argsToResolve = null;
        synchronized (mbd.constructorArgumentLock) {
            constructorToUse = (Constructor<?>) mbd.resolvedConstructorOrFactoryMethod;
            if (constructorToUse != null && mbd.constructorArgumentsResolved) {
                // Found a cached constructor...
                argsToUse = mbd.resolvedConstructorArguments;
                if (argsToUse == null) {
                    argsToResolve = mbd.preparedConstructorArguments;
                }
            }
        }
        if (argsToResolve != null) {
            argsToUse = resolvePreparedArguments(beanName, mbd, bw, constructorToUse, argsToResolve, true);
        }
    }

    if (constructorToUse == null) {
        // Need to resolve the constructor.
        boolean autowiring = (chosenCtors != null
                || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
        ConstructorArgumentValues resolvedValues = null;

        int minNrOfArgs;
        if (explicitArgs != null) {
            minNrOfArgs = explicitArgs.length;
        } else {
            ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
            resolvedValues = new ConstructorArgumentValues();
            minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
        }

        // Take specified constructors, if any.
        Constructor<?>[] candidates = chosenCtors;
        if (candidates == null) {
            Class<?> beanClass = mbd.getBeanClass();
            try {
                candidates = (mbd.isNonPublicAccessAllowed() ? beanClass.getDeclaredConstructors()
                        : beanClass.getConstructors());
            } catch (Throwable ex) {
                throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                        "Resolution of declared constructors on bean Class [" + beanClass.getName()
                                + "] from ClassLoader [" + beanClass.getClassLoader() + "] failed",
                        ex);
            }
        }
        AutowireUtils.sortConstructors(candidates);
        int minTypeDiffWeight = Integer.MAX_VALUE;
        Set<Constructor<?>> ambiguousConstructors = null;
        LinkedList<UnsatisfiedDependencyException> causes = null;

        for (Constructor<?> candidate : candidates) {
            Class<?>[] paramTypes = candidate.getParameterTypes();

            if (constructorToUse != null && argsToUse.length > paramTypes.length) {
                // Already found greedy constructor that can be satisfied ->
                // do not look any further, there are only less greedy constructors left.
                break;
            }
            if (paramTypes.length < minNrOfArgs) {
                continue;
            }

            ArgumentsHolder argsHolder;
            if (resolvedValues != null) {
                try {
                    String[] paramNames = ConstructorPropertiesChecker.evaluate(candidate, paramTypes.length);
                    if (paramNames == null) {
                        ParameterNameDiscoverer pnd = this.beanFactory.getParameterNameDiscoverer();
                        if (pnd != null) {
                            paramNames = pnd.getParameterNames(candidate);
                        }
                    }
                    argsHolder = createArgumentArray(beanName, mbd, resolvedValues, bw, paramTypes, paramNames,
                            getUserDeclaredConstructor(candidate), autowiring, candidates.length == 1);
                } catch (UnsatisfiedDependencyException ex) {
                    if (logger.isTraceEnabled()) {
                        logger.trace(
                                "Ignoring constructor [" + candidate + "] of bean '" + beanName + "': " + ex);
                    }
                    // Swallow and try next constructor.
                    if (causes == null) {
                        causes = new LinkedList<>();
                    }
                    causes.add(ex);
                    continue;
                }
            } else {
                // Explicit arguments given -> arguments length must match exactly.
                if (paramTypes.length != explicitArgs.length) {
                    continue;
                }
                argsHolder = new ArgumentsHolder(explicitArgs);
            }

            int typeDiffWeight = (mbd.isLenientConstructorResolution()
                    ? argsHolder.getTypeDifferenceWeight(paramTypes)
                    : argsHolder.getAssignabilityWeight(paramTypes));
            // Choose this constructor if it represents the closest match.
            if (typeDiffWeight < minTypeDiffWeight) {
                constructorToUse = candidate;
                argsHolderToUse = argsHolder;
                argsToUse = argsHolder.arguments;
                minTypeDiffWeight = typeDiffWeight;
                ambiguousConstructors = null;
            } else if (constructorToUse != null && typeDiffWeight == minTypeDiffWeight) {
                if (ambiguousConstructors == null) {
                    ambiguousConstructors = new LinkedHashSet<>();
                    ambiguousConstructors.add(constructorToUse);
                }
                ambiguousConstructors.add(candidate);
            }
        }

        if (constructorToUse == null) {
            if (causes != null) {
                UnsatisfiedDependencyException ex = causes.removeLast();
                for (Exception cause : causes) {
                    this.beanFactory.onSuppressedException(cause);
                }
                throw ex;
            }
            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                    "Could not resolve matching constructor "
                            + "(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)");
        } else if (ambiguousConstructors != null && !mbd.isLenientConstructorResolution()) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                    "Ambiguous constructor matches found in bean '" + beanName + "' "
                            + "(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities): "
                            + ambiguousConstructors);
        }

        if (explicitArgs == null) {
            argsHolderToUse.storeCache(mbd, constructorToUse);
        }
    }

    try {
        final InstantiationStrategy strategy = this.beanFactory.getInstantiationStrategy();
        Object beanInstance;

        if (System.getSecurityManager() != null) {
            final Constructor<?> ctorToUse = constructorToUse;
            final Object[] argumentsToUse = argsToUse;
            beanInstance = AccessController
                    .doPrivileged(
                            (PrivilegedAction<Object>) () -> strategy.instantiate(mbd, beanName,
                                    this.beanFactory, ctorToUse, argumentsToUse),
                            this.beanFactory.getAccessControlContext());
        } else {
            beanInstance = strategy.instantiate(mbd, beanName, this.beanFactory, constructorToUse, argsToUse);
        }

        bw.setBeanInstance(beanInstance);
        return bw;
    } catch (Throwable ex) {
        throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                "Bean instantiation via constructor failed", ex);
    }
}

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