/*
* Copyright 2009-2013 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.ibatis.executor.loader;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import org.apache.ibatis.executor.BaseExecutor;
import org.apache.ibatis.executor.BatchResult;
import org.apache.ibatis.executor.ExecutorException;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
/**
* @author Clinton Begin
* @author Franta Mejta
*/
/**
* 结果延迟加载器映射
*
*/
public class ResultLoaderMap {
//加载对的hashmap
private final Map<String, LoadPair> loaderMap = new HashMap<String, LoadPair>();
//把要延迟加载的属性记到ResultLoaderMap里（一个哈希表）
public void addLoader(String property, MetaObject metaResultObject, ResultLoader resultLoader) {
String upperFirst = getUppercaseFirstProperty(property);
if (!upperFirst.equalsIgnoreCase(property) && loaderMap.containsKey(upperFirst)) {
throw new ExecutorException("Nested lazy loaded result property '" + property +
"' for query id '" + resultLoader.mappedStatement.getId() +
" already exists in the result map. The leftmost property of all lazy loaded properties must be unique within a result map.");
}
//key是property，这样当客户端调用getter来取真实值时，会判断这个属性是否是延迟加载属性，是才去加载
//可参见CglibProxyFactory的代码
// if (lazyLoader.hasLoader(property)) {
// lazyLoader.load(property);
// }
loaderMap.put(upperFirst, new LoadPair(property, metaResultObject, resultLoader));
}
public final Map<String, LoadPair> getProperties() {
return new HashMap<String, LoadPair>(this.loaderMap);
}
public Set<String> getPropertyNames() {
return loaderMap.keySet();
}
public int size() {
return loaderMap.size();
}
public boolean hasLoader(String property) {
return loaderMap.containsKey(property.toUpperCase(Locale.ENGLISH));
}
public boolean load(String property) throws SQLException {
//先删除key，防止第二次又去查数据库就不对了
LoadPair pair = loaderMap.remove(property.toUpperCase(Locale.ENGLISH));
if (pair != null) {
//去数据库查
pair.load();
return true;
}
return false;
}
public void loadAll() throws SQLException {
final Set<String> methodNameSet = loaderMap.keySet();
String[] methodNames = methodNameSet.toArray(new String[methodNameSet.size()]);
for (String methodName : methodNames) {
load(methodName);
}
}
private static String getUppercaseFirstProperty(String property) {
String[] parts = property.split("\\.");
return parts[0].toUpperCase(Locale.ENGLISH);
}
/**
* Property which was not loaded yet.
*/
//静态内部类，加载对
public static class LoadPair implements Serializable {
private static final long serialVersionUID = 20130412;
/**
* Name of factory method which returns database connection.
*/
private static final String FACTORY_METHOD = "getConfiguration";
/**
* Object to check whether we went through serialization..
*/
private final transient Object serializationCheck = new Object();
/**
* Meta object which sets loaded properties.
*/
private transient MetaObject metaResultObject;
/**
* Result loader which loads unread properties.
*/
private transient ResultLoader resultLoader;
/**
* Wow, logger.
*/
private transient Log log;
/**
* Factory class through which we get database connection.
*/
private Class<?> configurationFactory;
/**
* Name of the unread property.
*/
private String property;
/**
* ID of SQL statement which loads the property.
*/
private String mappedStatement;
/**
* Parameter of the sql statement.
*/
private Serializable mappedParameter;
private LoadPair(final String property, MetaObject metaResultObject, ResultLoader resultLoader) {
this.property = property;
this.metaResultObject = metaResultObject;
this.resultLoader = resultLoader;
/* Save required information only if original object can be serialized. */
if (metaResultObject != null && metaResultObject.getOriginalObject() instanceof Serializable) {
final Object mappedStatementParameter = resultLoader.parameterObject;
/* @todo May the parameter be null? */
if (mappedStatementParameter instanceof Serializable) {
this.mappedStatement = resultLoader.mappedStatement.getId();
this.mappedParameter = (Serializable) mappedStatementParameter;
this.configurationFactory = resultLoader.configuration.getConfigurationFactory();
} else {
this.getLogger().debug("Property [" + this.property + "] of ["
+ metaResultObject.getOriginalObject().getClass() + "] cannot be loaded "
+ "after deserialization. Make sure it's loaded before serializing "
+ "forenamed object.");
}
}
}
public void load() throws SQLException {
/* These field should not be null unless the loadpair was serialized.
* Yet in that case this method should not be called. */
if (this.metaResultObject == null) {
throw new IllegalArgumentException("metaResultObject is null");
}
if (this.resultLoader == null) {
throw new IllegalArgumentException("resultLoader is null");
}
this.load(null);
}
public void load(final Object userObject) throws SQLException {
if (this.metaResultObject == null || this.resultLoader == null) {
if (this.mappedParameter == null) {
throw new ExecutorException("Property [" + this.property + "] cannot be loaded because "
+ "required parameter of mapped statement ["
+ this.mappedStatement + "] is not serializable.");
}
final Configuration config = this.getConfiguration();
final MappedStatement ms = config.getMappedStatement(this.mappedStatement);
if (ms == null) {
throw new ExecutorException("Cannot lazy load property [" + this.property
+ "] of deserialized object [" + userObject.getClass()
+ "] because configuration does not contain statement ["
+ this.mappedStatement + "]");
}
this.metaResultObject = config.newMetaObject(userObject);
this.resultLoader = new ResultLoader(config, new ClosedExecutor(), ms, this.mappedParameter,
metaResultObject.getSetterType(this.property), null, null);
}
/* We are using a new executor because we may be (and likely are) on a new thread
* and executors aren't thread safe. (Is this sufficient?)
*
* A better approach would be making executors thread safe. */
if (this.serializationCheck == null) {
final ResultLoader old = this.resultLoader;
this.resultLoader = new ResultLoader(old.configuration, new ClosedExecutor(), old.mappedStatement,
old.parameterObject, old.targetType, old.cacheKey, old.boundSql);
}
this.metaResultObject.setValue(property, this.resultLoader.loadResult());
}
private Configuration getConfiguration() {
if (this.configurationFactory == null) {
throw new ExecutorException("Cannot get Configuration as configuration factory was not set.");
}
Object configurationObject = null;
try {
final Method factoryMethod = this.configurationFactory.getDeclaredMethod(FACTORY_METHOD);
if (!Modifier.isStatic(factoryMethod.getModifiers())) {
throw new ExecutorException("Cannot get Configuration as factory method ["
+ this.configurationFactory + "]#["
+ FACTORY_METHOD + "] is not static.");
}
if (!factoryMethod.isAccessible()) {
configurationObject = AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
@Override
public Object run() throws Exception {
try {
factoryMethod.setAccessible(true);
return factoryMethod.invoke(null);
} finally {
factoryMethod.setAccessible(false);
}
}
});
} else {
configurationObject = factoryMethod.invoke(null);
}
} catch (final NoSuchMethodException ex) {
throw new ExecutorException("Cannot get Configuration as factory class ["
+ this.configurationFactory + "] is missing factory method of name ["
+ FACTORY_METHOD + "].", ex);
} catch (final PrivilegedActionException ex) {
throw new ExecutorException("Cannot get Configuration as factory method ["
+ this.configurationFactory + "]#["
+ FACTORY_METHOD + "] threw an exception.", ex.getCause());
} catch (final Exception ex) {
throw new ExecutorException("Cannot get Configuration as factory method ["
+ this.configurationFactory + "]#["
+ FACTORY_METHOD + "] threw an exception.", ex);
}
if (!(configurationObject instanceof Configuration)) {
throw new ExecutorException("Cannot get Configuration as factory method ["
+ this.configurationFactory + "]#["
+ FACTORY_METHOD + "] didn't return [" + Configuration.class + "] but ["
+ (configurationObject == null ? "null" : configurationObject.getClass()) + "].");
}
return Configuration.class.cast(configurationObject);
}
private Log getLogger() {
if (this.log == null) {
this.log = LogFactory.getLog(this.getClass());
}
return this.log;
}
}
private static final class ClosedExecutor extends BaseExecutor {
public ClosedExecutor() {
super(null, null);
}
@Override
public boolean isClosed() {
return true;
}
@Override
protected int doUpdate(MappedStatement ms, Object parameter) throws SQLException {
throw new UnsupportedOperationException("Not supported.");
}
@Override
protected List<BatchResult> doFlushStatements(boolean isRollback) throws SQLException {
throw new UnsupportedOperationException("Not supported.");
}
@Override
protected <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
throw new UnsupportedOperationException("Not supported.");
}
}
}