/*
* 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.builder.xml;
import java.io.InputStream;
import java.io.Reader;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import org.apache.ibatis.builder.BaseBuilder;
import org.apache.ibatis.builder.BuilderException;
import org.apache.ibatis.builder.CacheRefResolver;
import org.apache.ibatis.builder.IncompleteElementException;
import org.apache.ibatis.builder.MapperBuilderAssistant;
import org.apache.ibatis.builder.ResultMapResolver;
import org.apache.ibatis.cache.Cache;
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.mapping.Discriminator;
import org.apache.ibatis.mapping.ParameterMapping;
import org.apache.ibatis.mapping.ParameterMode;
import org.apache.ibatis.mapping.ResultFlag;
import org.apache.ibatis.mapping.ResultMap;
import org.apache.ibatis.mapping.ResultMapping;
import org.apache.ibatis.parsing.XNode;
import org.apache.ibatis.parsing.XPathParser;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.TypeHandler;
/**
* @author Clinton Begin
*/
/**
* XML映射构建器,建造者模式,继承BaseBuilder
*
*/
public class XMLMapperBuilder extends BaseBuilder {
private XPathParser parser;
//映射器构建助手
private MapperBuilderAssistant builderAssistant;
//用来存放sql片段的哈希表
private Map<String, XNode> sqlFragments;
private String resource;
@Deprecated
public XMLMapperBuilder(Reader reader, Configuration configuration, String resource, Map<String, XNode> sqlFragments, String namespace) {
this(reader, configuration, resource, sqlFragments);
this.builderAssistant.setCurrentNamespace(namespace);
}
@Deprecated
public XMLMapperBuilder(Reader reader, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
this(new XPathParser(reader, true, configuration.getVariables(), new XMLMapperEntityResolver()),
configuration, resource, sqlFragments);
}
public XMLMapperBuilder(InputStream inputStream, Configuration configuration, String resource, Map<String, XNode> sqlFragments, String namespace) {
this(inputStream, configuration, resource, sqlFragments);
this.builderAssistant.setCurrentNamespace(namespace);
}
public XMLMapperBuilder(InputStream inputStream, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
this(new XPathParser(inputStream, true, configuration.getVariables(), new XMLMapperEntityResolver()),
configuration, resource, sqlFragments);
}
private XMLMapperBuilder(XPathParser parser, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
super(configuration);
this.builderAssistant = new MapperBuilderAssistant(configuration, resource);
this.parser = parser;
this.sqlFragments = sqlFragments;
this.resource = resource;
}
//解析
public void parse() {
//如果没有加载过再加载,防止重复加载
if (!configuration.isResourceLoaded(resource)) {
//配置mapper
configurationElement(parser.evalNode("/mapper"));
//标记一下,已经加载过了
configuration.addLoadedResource(resource);
//绑定映射器到namespace
bindMapperForNamespace();
}
//还有没解析完的东东这里接着解析?
parsePendingResultMaps();
parsePendingChacheRefs();
parsePendingStatements();
}
public XNode getSqlFragment(String refid) {
return sqlFragments.get(refid);
}
//配置mapper元素
// <mapper namespace="org.mybatis.example.BlogMapper">
// <select id="selectBlog" parameterType="int" resultType="Blog">
// select * from Blog where id = #{id}
// </select>
// </mapper>
private void configurationElement(XNode context) {
try {
//1.配置namespace
String namespace = context.getStringAttribute("namespace");
if (namespace.equals("")) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
builderAssistant.setCurrentNamespace(namespace);
//2.配置cache-ref
cacheRefElement(context.evalNode("cache-ref"));
//3.配置cache
cacheElement(context.evalNode("cache"));
//4.配置parameterMap(已经废弃,老式风格的参数映射)
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
//5.配置resultMap(高级功能)
resultMapElements(context.evalNodes("/mapper/resultMap"));
//6.配置sql(定义可重用的 SQL 代码段)
sqlElement(context.evalNodes("/mapper/sql"));
//7.配置select|insert|update|delete TODO
buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {
throw new BuilderException("Error parsing Mapper XML. Cause: " + e, e);
}
}
//7.配置select|insert|update|delete
private void buildStatementFromContext(List<XNode> list) {
//调用7.1构建语句
if (configuration.getDatabaseId() != null) {
buildStatementFromContext(list, configuration.getDatabaseId());
}
buildStatementFromContext(list, null);
}
//7.1构建语句
private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
for (XNode context : list) {
//构建所有语句,一个mapper下可以有很多select
//语句比较复杂,核心都在这里面,所以调用XMLStatementBuilder
final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
try {
//核心XMLStatementBuilder.parseStatementNode
statementParser.parseStatementNode();
} catch (IncompleteElementException e) {
//如果出现SQL语句不完整,把它记下来,塞到configuration去
configuration.addIncompleteStatement(statementParser);
}
}
}
private void parsePendingResultMaps() {
Collection<ResultMapResolver> incompleteResultMaps = configuration.getIncompleteResultMaps();
synchronized (incompleteResultMaps) {
Iterator<ResultMapResolver> iter = incompleteResultMaps.iterator();
while (iter.hasNext()) {
try {
iter.next().resolve();
iter.remove();
} catch (IncompleteElementException e) {
// ResultMap is still missing a resource...
}
}
}
}
private void parsePendingChacheRefs() {
Collection<CacheRefResolver> incompleteCacheRefs = configuration.getIncompleteCacheRefs();
synchronized (incompleteCacheRefs) {
Iterator<CacheRefResolver> iter = incompleteCacheRefs.iterator();
while (iter.hasNext()) {
try {
iter.next().resolveCacheRef();
iter.remove();
} catch (IncompleteElementException e) {
// Cache ref is still missing a resource...
}
}
}
}
private void parsePendingStatements() {
Collection<XMLStatementBuilder> incompleteStatements = configuration.getIncompleteStatements();
synchronized (incompleteStatements) {
Iterator<XMLStatementBuilder> iter = incompleteStatements.iterator();
while (iter.hasNext()) {
try {
iter.next().parseStatementNode();
iter.remove();
} catch (IncompleteElementException e) {
// Statement is still missing a resource...
}
}
}
}
//2.配置cache-ref,在这样的 情况下你可以使用 cache-ref 元素来引用另外一个缓存。
//<cache-ref namespace="com.someone.application.data.SomeMapper"/>
private void cacheRefElement(XNode context) {
if (context != null) {
//增加cache-ref
configuration.addCacheRef(builderAssistant.getCurrentNamespace(), context.getStringAttribute("namespace"));
CacheRefResolver cacheRefResolver = new CacheRefResolver(builderAssistant, context.getStringAttribute("namespace"));
try {
cacheRefResolver.resolveCacheRef();
} catch (IncompleteElementException e) {
configuration.addIncompleteCacheRef(cacheRefResolver);
}
}
}
//3.配置cache
// <cache
// eviction="FIFO"
// flushInterval="60000"
// size="512"
// readOnly="true"/>
private void cacheElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type", "PERPETUAL");
Class<? extends Cache> typeClass = typeAliasRegistry.resolveAlias(type);
String eviction = context.getStringAttribute("eviction", "LRU");
Class<? extends Cache> evictionClass = typeAliasRegistry.resolveAlias(eviction);
Long flushInterval = context.getLongAttribute("flushInterval");
Integer size = context.getIntAttribute("size");
boolean readWrite = !context.getBooleanAttribute("readOnly", false);
boolean blocking = context.getBooleanAttribute("blocking", false);
//读入额外的配置信息,易于第三方的缓存扩展,例:
// <cache type="com.domain.something.MyCustomCache">
// <property name="cacheFile" value="/tmp/my-custom-cache.tmp"/>
// </cache>
Properties props = context.getChildrenAsProperties();
//调用builderAssistant.useNewCache
builderAssistant.useNewCache(typeClass, evictionClass, flushInterval, size, readWrite, blocking, props);
}
}
//4.配置parameterMap
//已经被废弃了!老式风格的参数映射。可以忽略
private void parameterMapElement(List<XNode> list) throws Exception {
for (XNode parameterMapNode : list) {
String id = parameterMapNode.getStringAttribute("id");
String type = parameterMapNode.getStringAttribute("type");
Class<?> parameterClass = resolveClass(type);
List<XNode> parameterNodes = parameterMapNode.evalNodes("parameter");
List<ParameterMapping> parameterMappings = new ArrayList<ParameterMapping>();
for (XNode parameterNode : parameterNodes) {
String property = parameterNode.getStringAttribute("property");
String javaType = parameterNode.getStringAttribute("javaType");
String jdbcType = parameterNode.getStringAttribute("jdbcType");
String resultMap = parameterNode.getStringAttribute("resultMap");
String mode = parameterNode.getStringAttribute("mode");
String typeHandler = parameterNode.getStringAttribute("typeHandler");
Integer numericScale = parameterNode.getIntAttribute("numericScale");
ParameterMode modeEnum = resolveParameterMode(mode);
Class<?> javaTypeClass = resolveClass(javaType);
JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
@SuppressWarnings("unchecked")
Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
ParameterMapping parameterMapping = builderAssistant.buildParameterMapping(parameterClass, property, javaTypeClass, jdbcTypeEnum, resultMap, modeEnum, typeHandlerClass, numericScale);
parameterMappings.add(parameterMapping);
}
builderAssistant.addParameterMap(id, parameterClass, parameterMappings);
}
}
//5.配置resultMap,高级功能
private void resultMapElements(List<XNode> list) throws Exception {
//基本上就是循环把resultMap加入到Configuration里去,保持2份,一份缩略,一分全名
for (XNode resultMapNode : list) {
try {
//循环调resultMapElement
resultMapElement(resultMapNode);
} catch (IncompleteElementException e) {
// ignore, it will be retried
}
}
}
//5.1 配置resultMap
private ResultMap resultMapElement(XNode resultMapNode) throws Exception {
return resultMapElement(resultMapNode, Collections.<ResultMapping> emptyList());
}
//5.1 配置resultMap
private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> additionalResultMappings) throws Exception {
//错误上下文
//取得标示符 ("resultMap[userResultMap]")
// <resultMap id="userResultMap" type="User">
// <id property="id" column="user_id" />
// <result property="username" column="username"/>
// <result property="password" column="password"/>
// </resultMap>
ErrorContext.instance().activity("processing " + resultMapNode.getValueBasedIdentifier());
String id = resultMapNode.getStringAttribute("id",
resultMapNode.getValueBasedIdentifier());
//一般拿type就可以了,后面3个难道是兼容老的代码?
String type = resultMapNode.getStringAttribute("type",
resultMapNode.getStringAttribute("ofType",
resultMapNode.getStringAttribute("resultType",
resultMapNode.getStringAttribute("javaType"))));
//高级功能,还支持继承?
// <resultMap id="carResult" type="Car" extends="vehicleResult">
// <result property="doorCount" column="door_count" />
// </resultMap>
String extend = resultMapNode.getStringAttribute("extends");
//autoMapping
Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping");
Class<?> typeClass = resolveClass(type);
Discriminator discriminator = null;
List<ResultMapping> resultMappings = new ArrayList<ResultMapping>();
resultMappings.addAll(additionalResultMappings);
List<XNode> resultChildren = resultMapNode.getChildren();
for (XNode resultChild : resultChildren) {
if ("constructor".equals(resultChild.getName())) {
//解析result map的constructor
processConstructorElement(resultChild, typeClass, resultMappings);
} else if ("discriminator".equals(resultChild.getName())) {
//解析result map的discriminator
discriminator = processDiscriminatorElement(resultChild, typeClass, resultMappings);
} else {
List<ResultFlag> flags = new ArrayList<ResultFlag>();
if ("id".equals(resultChild.getName())) {
flags.add(ResultFlag.ID);
}
//调5.1.1 buildResultMappingFromContext,得到ResultMapping
resultMappings.add(buildResultMappingFromContext(resultChild, typeClass, flags));
}
}
//最后再调ResultMapResolver得到ResultMap
ResultMapResolver resultMapResolver = new ResultMapResolver(builderAssistant, id, typeClass, extend, discriminator, resultMappings, autoMapping);
try {
return resultMapResolver.resolve();
} catch (IncompleteElementException e) {
configuration.addIncompleteResultMap(resultMapResolver);
throw e;
}
}
//解析result map的constructor
//<constructor>
// <idArg column="blog_id" javaType="int"/>
//</constructor>
private void processConstructorElement(XNode resultChild, Class<?> resultType, List<ResultMapping> resultMappings) throws Exception {
List<XNode> argChildren = resultChild.getChildren();
for (XNode argChild : argChildren) {
List<ResultFlag> flags = new ArrayList<ResultFlag>();
//结果标志加上ID和CONSTRUCTOR
flags.add(ResultFlag.CONSTRUCTOR);
if ("idArg".equals(argChild.getName())) {
flags.add(ResultFlag.ID);
}
resultMappings.add(buildResultMappingFromContext(argChild, resultType, flags));
}
}
//解析result map的discriminator
//<discriminator javaType="int" column="draft">
// <case value="1" resultType="DraftPost"/>
//</discriminator>
private Discriminator processDiscriminatorElement(XNode context, Class<?> resultType, List<ResultMapping> resultMappings) throws Exception {
String column = context.getStringAttribute("column");
String javaType = context.getStringAttribute("javaType");
String jdbcType = context.getStringAttribute("jdbcType");
String typeHandler = context.getStringAttribute("typeHandler");
Class<?> javaTypeClass = resolveClass(javaType);
@SuppressWarnings("unchecked")
Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
Map<String, String> discriminatorMap = new HashMap<String, String>();
for (XNode caseChild : context.getChildren()) {
String value = caseChild.getStringAttribute("value");
String resultMap = caseChild.getStringAttribute("resultMap", processNestedResultMappings(caseChild, resultMappings));
discriminatorMap.put(value, resultMap);
}
return builderAssistant.buildDiscriminator(resultType, column, javaTypeClass, jdbcTypeEnum, typeHandlerClass, discriminatorMap);
}
//6 配置sql(定义可重用的 SQL 代码段)
private void sqlElement(List<XNode> list) throws Exception {
if (configuration.getDatabaseId() != null) {
sqlElement(list, configuration.getDatabaseId());
}
sqlElement(list, null);
}
//6.1 配置sql
//<sql id="userColumns"> id,username,password </sql>
private void sqlElement(List<XNode> list, String requiredDatabaseId) throws Exception {
for (XNode context : list) {
String databaseId = context.getStringAttribute("databaseId");
String id = context.getStringAttribute("id");
id = builderAssistant.applyCurrentNamespace(id, false);
//比较简单,就是将sql片段放入hashmap,不过此时还没有解析sql片段
if (databaseIdMatchesCurrent(id, databaseId, requiredDatabaseId)) {
sqlFragments.put(id, context);
}
}
}
private boolean databaseIdMatchesCurrent(String id, String databaseId, String requiredDatabaseId) {
if (requiredDatabaseId != null) {
if (!requiredDatabaseId.equals(databaseId)) {
return false;
}
} else {
if (databaseId != null) {
return false;
}
// skip this fragment if there is a previous one with a not null databaseId
//如果有重名的id了
//<sql id="userColumns"> id,username,password </sql>
if (this.sqlFragments.containsKey(id)) {
XNode context = this.sqlFragments.get(id);
//如果之前那个重名的sql id有databaseId,则false,否则难道true?这样新的sql覆盖老的sql???
if (context.getStringAttribute("databaseId") != null) {
return false;
}
}
}
return true;
}
//5.1.1 构建resultMap
private ResultMapping buildResultMappingFromContext(XNode context, Class<?> resultType, List<ResultFlag> flags) throws Exception {
//<id property="id" column="author_id"/>
//<result property="username" column="author_username"/>
String property = context.getStringAttribute("property");
String column = context.getStringAttribute("column");
String javaType = context.getStringAttribute("javaType");
String jdbcType = context.getStringAttribute("jdbcType");
String nestedSelect = context.getStringAttribute("select");
//处理嵌套的result map
String nestedResultMap = context.getStringAttribute("resultMap",
processNestedResultMappings(context, Collections.<ResultMapping> emptyList()));
String notNullColumn = context.getStringAttribute("notNullColumn");
String columnPrefix = context.getStringAttribute("columnPrefix");
String typeHandler = context.getStringAttribute("typeHandler");
String resulSet = context.getStringAttribute("resultSet");
String foreignColumn = context.getStringAttribute("foreignColumn");
boolean lazy = "lazy".equals(context.getStringAttribute("fetchType", configuration.isLazyLoadingEnabled() ? "lazy" : "eager"));
Class<?> javaTypeClass = resolveClass(javaType);
@SuppressWarnings("unchecked")
Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
//又去调builderAssistant.buildResultMapping
return builderAssistant.buildResultMapping(resultType, property, column, javaTypeClass, jdbcTypeEnum, nestedSelect, nestedResultMap, notNullColumn, columnPrefix, typeHandlerClass, flags, resulSet, foreignColumn, lazy);
}
//5.1.1.1 处理嵌套的result map
private String processNestedResultMappings(XNode context, List<ResultMapping> resultMappings) throws Exception {
//处理association|collection|case
if ("association".equals(context.getName())
|| "collection".equals(context.getName())
|| "case".equals(context.getName())) {
// <resultMap id="blogResult" type="Blog">
// <association property="author" column="author_id" javaType="Author" select="selectAuthor"/>
// </resultMap>
//如果不是嵌套查询
if (context.getStringAttribute("select") == null) {
//则递归调用5.1 resultMapElement
ResultMap resultMap = resultMapElement(context, resultMappings);
return resultMap.getId();
}
}
return null;
}
private void bindMapperForNamespace() {
String namespace = builderAssistant.getCurrentNamespace();
if (namespace != null) {
Class<?> boundType = null;
try {
boundType = Resources.classForName(namespace);
} catch (ClassNotFoundException e) {
//ignore, bound type is not required
}
if (boundType != null) {
if (!configuration.hasMapper(boundType)) {
// Spring may not know the real resource name so we set a flag
// to prevent loading again this resource from the mapper interface
// look at MapperAnnotationBuilder#loadXmlResource
configuration.addLoadedResource("namespace:" + namespace);
configuration.addMapper(boundType);
}
}
}
}
}