wamblee.org Git - utils/blob - system/general/src/main/java/org/wamblee/system/adapters/ConstructorConfiguration.java

   1 /*
   2  * Copyright 2008 the original author or authors.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *      http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package org.wamblee.system.adapters;
  17
  18 import java.lang.reflect.Constructor;
  19 import java.lang.reflect.Modifier;
  20 import java.util.ArrayList;
  21 import java.util.Arrays;
  22 import java.util.List;
  23
  24 import org.wamblee.collections.CollectionFilter;
  25 import org.wamblee.conditions.Condition;
  26 import org.wamblee.system.core.RequiredInterface;
  27 import org.wamblee.system.core.Scope;
  28 import org.wamblee.system.core.SystemAssemblyException;
  29
  30 /**
  31  * Class that allows configuration of the constructor to use.
  32  *
  33  * In particular, it provides:
  34  * <ul>
  35  *   <li> Selection of a constructor using explicit selection
  36  *      {@link #select(Class...)} or using the most greedy constructor
  37  *      {@link #greedy()}.
  38  *   </li>
  39  *   <li>
  40  *      Selection of methods to invoke to inject other objects into the object.
  41  *   </li>
  42  *   <li> Selection of fields to set.
  43  *   </li>
  44  * </ul>
  45  */
  46 public class ConstructorConfiguration {
  47         private Class clazz;
  48         private Constructor<?> constructor;
  49         private ParameterValues values;
  50         private boolean publicOnly;
  51
  52         /**
  53          * Constructs the configuration. By default the public constructor with the
  54          * most arguments will be used.
  55          * @param aClass Class to construct.
  56          */
  57         public ConstructorConfiguration(Class aClass) {
  58                 clazz = aClass;
  59                 constructor = null;
  60                 publicOnly = true;
  61         }
  62
  63         /**
  64          * Sets whether or no non public constructors are also considered.
  65          * Reset the choice of a constructor to its default.
  66          * @param aNonPublic
  67          * @return
  68          */
  69         public ConstructorConfiguration setNonPublic(boolean aNonPublic) {
  70                 publicOnly = !aNonPublic;
  71                 constructor = null;
  72                 values = null;
  73                 return this;
  74         }
  75
  76         /**
  77          * Selects an explicit constructor.
  78          * @param aTypes Arguments of the constructor.
  79          * @return Return the injector to allow call chaining.
  80          */
  81         public ConstructorConfiguration select(Class... aTypes) {
  82                 try {
  83                         constructor = clazz.getDeclaredConstructor(aTypes);
  84                 } catch (Exception e) {
  85                         throw new SystemAssemblyException(e.getMessage(), e);
  86                 }
  87                 resetValues();
  88                 return this;
  89         }
  90
  91         /**
  92          * Selects the greediest constructor.
  93          * @return The injector to allow call chaining.
  94          * @throws SystemAssemblyException if the greediest constructor cannot be uniquely
  95          *    identified.
  96          */
  97         public ConstructorConfiguration greedy() {
  98                 Constructor<?>[] declared = clazz.getDeclaredConstructors();
  99                 if (declared.length == 0) {
 100                         throw new SystemAssemblyException("Class '" + clazz
 101                                         + " is an interface, primitive type, or array");
 102                 }
 103                 int max = -1;
 104                 List<Constructor<?>> checked = new ArrayList<Constructor<?>>();
 105                 CollectionFilter.filter(Arrays.asList(declared), checked,
 106                         new Condition<Constructor<?>>() {
 107                         @Override
 108                         public boolean matches(Constructor<?> aObject) {
 109                                 if ( !publicOnly ) {
 110                                         return true;
 111                                 } else {
 112                                         return Modifier.isPublic(aObject.getModifiers());
 113                                 }
 114                         }
 115                 });
 116                 for (Constructor ctor : checked) {
 117                         if (ctor.getParameterTypes().length > max) {
 118                                 max = ctor.getParameterTypes().length;
 119                         }
 120                 }
 121                 final int max2 = max;
 122                 List<Constructor<?>> ctors = checked;
 123                 List<Constructor<?>> longest = new ArrayList<Constructor<?>>();
 124                 CollectionFilter.filter(ctors, longest,
 125                                 new Condition<Constructor<?>>() {
 126                                         @Override
 127                                         public boolean matches(Constructor<?> aObject) {
 128                                                 return aObject.getParameterTypes().length == max2;
 129                                         }
 130                                 });
 131                 if (longest.size() > 1) {
 132                         throw new SystemAssemblyException(
 133                                         "Greediest constructor cannot be uniquely determined");
 134                 }
 135             constructor = longest.get(0);
 136             resetValues();
 137             return this;
 138         }
 139
 140         public ParameterValues getParameters() {
 141                 getConstructor(); // initialize constructor if needed.
 142                 return values;
 143         }
 144
 145         /**
 146          * Resets the values.
 147          */
 148         private void resetValues() {
 149                 constructor.setAccessible(true);
 150                 values = new ParameterValues(constructor.getParameterTypes());
 151         }
 152
 153         /**
 154          * Creates the object in the given scope.
 155          * @param aScope Scope containing required interfaces for this object.
 156          * @return object.
 157          */
 158         public Object create(Scope aScope) {
 159                 Object[] valueArray = values.values(aScope);
 160                 try {
 161                         return getConstructor().newInstance(valueArray);
 162                 } catch (Exception e) {
 163                         throw new SystemAssemblyException("Could not construct object "
 164                                         + getConstructor() + " " + Arrays.asList(valueArray), e);
 165                 }
 166         }
 167
 168         public List<RequiredInterface> getRequiredInterfaces() {
 169                 getConstructor(); // initialize constructor if needed.
 170                 return values.getRequiredInterfaces();
 171         }
 172
 173         private Constructor getConstructor() {
 174                 if (constructor == null ) {
 175                         greedy();
 176                 }
 177                 return constructor;
 178         }
 179 }