最基本的连接数据库驱动代码：
public static void main(String[] args) throws Exception {
// 第一步
Connection root =
DriverManager.getConnection("jdbc:mysql://localhost:3306/mybatisMy?characterEncoding=utf-8", "root", "123456");
// 第二步
PreparedStatement preparedStatement = root.prepareStatement("select * from test where id=?");
// 第三步
preparedStatement.setString(1,"2");
//第四步
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
String columnName1 = resultSet.getMetaData().getColumnName(1);
String columnName2 = resultSet.getMetaData().getColumnName(2);
System.out.println(columnName1+":"+resultSet.getString(1));
System.out.println(columnName2+":"+resultSet.getString(2));
}
resultSet.close();
preparedStatement.close();
root.close();
}mybatis的基本语法：
mybatis.xml和DemoMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!--<objectFactory type="com" >-->
<!--<property name="" value=""></property>-->
<!--</objectFactory>-->
<!-- 和spring整合后 environments配置将废除 -->
<environments default="development">
<environment id="development">
<!-- 使用jdbc事务管理 -->
<transactionManager type="JDBC" />
<!-- 数据库连接池 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url"
value="jdbc:mysql://localhost:3306/mybatisMy?characterEncoding=utf-8" />
<property name="username" value="root" />
<property name="password" value="123456" />
</dataSource>
</environment>
</environments>
<!-- 加载mapper.xml -->
<mappers>
<mapper resource="mapper/DemoMapper.xml" ></mapper>
<package name=""></package>
</mappers>
</configuration>
----------------------------------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.DemoMapper">
<select id="selectAll" parameterType="Map" resultType="Map">
select * from test WHERE id =#{id}
</select>
<!---->
<!---->
<!--<resultMap id="" type=""></resultMap>-->
<!---->
<!--<resultMap id="" type=""></resultMap>-->
</mapper>
public static void main(String[] args) throws Exception {
String resource = "mybatis.xml";
// 获得xmkl的输入流
InputStream inputStream = Resources.getResourceAsStream(resource);
// 获得连接工厂
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
//从调用者角度来讲 与数据库打交道的对象 SqlSession
//通过动态代理 去帮我们执行SQL
DemoMapper mapper = sqlSession.getMapper(DemoMapper.class);
Map<String,Object> map = new HashMap<>();
map.put("id","1");
System.out.println(mapper.selectAll(map));
sqlSession.close();
}进入build方法，进入parser.parse()方法，进入parseConfiguration方法，如何解析节点的？
private void parseConfiguration(XNode root) {
try {
//issue #117 read properties first
propertiesElement(root.evalNode("properties"));
Properties settings = settingsAsProperties(root.evalNode("settings"));
loadCustomVfs(settings);
loadCustomLogImpl(settings);
// 所谓别名 其实就是吧你指定的别名对应的class存储在一个Map当中 进入这个：注册别名方法1
typeAliasesElement(root.evalNode("typeAliases"));
pluginElement(root.evalNode("plugins"));
//objectFactory自定义实例化对象的行为 比如说返回User 对象 这个用的很少的
objectFactoryElement(root.evalNode("objectFactory"));
//MateObject 方便反射操作实体类的对象
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
settingsElement(settings);
// 解析JDBC的节点
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
// 这个要详细的解释以一下：解析mapper方法2
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}注册别名方法1：别名也可以在注解里面加载//@Alias("DemoMapper")
private void typeAliasesElement(XNode parent) {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {
String typeAliasPackage = child.getStringAttribute("name");
configuration.getTypeAliasRegistry().registerAliases(typeAliasPackage);
} else {
String alias = child.getStringAttribute("alias");
String type = child.getStringAttribute("type");
// com.luban.DemoMapper alias = DemoMapper type :com.luban.DemoMapper
try {
Class<?> clazz = Resources.classForName(type);
if (alias == null) {
typeAliasRegistry.registerAlias(clazz);// 别名方法1
} else {
typeAliasRegistry.registerAlias(alias, clazz);
}
} catch (ClassNotFoundException e) {
throw new BuilderException("Error registering typeAlias for '" + alias + "'. Cause: " + e, e);
}
}
}
}
}别名方法1：
public void registerAlias(String alias, Class<?> value) {
if (alias == null) {
throw new TypeException("The parameter alias cannot be null");
}
// issue #748 不区分大小写 Map ---> java.util.Map
String key = alias.toLowerCase(Locale.ENGLISH);
if (typeAliases.containsKey(key) && typeAliases.get(key) != null && !typeAliases.get(key).equals(value)) {
throw new TypeException("The alias '" + alias + "' is already mapped to the value '" + typeAliases.get(key).getName() + "'.");
}
typeAliases.put(key, value);
}解析mapper方法2：
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
//遍历解析mappers节点
for (XNode child : parent.getChildren()) {
//首先解析package节点 到底是解析注解还是解析xml
if ("package".equals(child.getName())) {
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);
} else {
//三个值只能有一个值是有值的 resource url class这个是mapper的配置方式
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
String mapperClass = child.getStringAttribute("class");
if (resource != null && url == null && mapperClass == null) {
ErrorContext.instance().resource(resource);
InputStream inputStream = Resources.getResourceAsStream(resource);
//解析resource.xml
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
mapperParser.parse();
} else if (resource == null && url != null && mapperClass == null) {
ErrorContext.instance().resource(url);
InputStream inputStream = Resources.getUrlAsStream(url);
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
// 方法：解析xml1
mapperParser.parse();
} else if (resource == null && url == null && mapperClass != null) {
Class<?> mapperInterface = Resources.classForName(mapperClass);
configuration.addMapper(mapperInterface);
} else {
throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
}
}
}
}
}解析的话把我们的mybatis.xml和mapper都解析了，因为mybatis.xml是包含mapper下面的xml的。
解析xml1：
锚点3：
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
// 方法：在这里面解析xml文件1
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
//绑定Namespace里面的Class对象
bindMapperForNamespace();
}
//重新解析之前解析不了的节点
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}锚点1：在这里面解析xml文件1：注意我们最终封装为mapperedStatement对象。
//解析mapper文件里面的节点
// 拿到里面配置的配置项 最终封装成一个MapperedStatemanet
private void configurationElement(XNode context) {
try {
String namespace = context.getStringAttribute("namespace");
if (namespace == null || namespace.equals("")) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
builderAssistant.setCurrentNamespace(namespace);
cacheRefElement(context.evalNode("cache-ref"));
cacheElement(context.evalNode("cache"));
// 方法：解析参数别名等1 别名用type表示
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
resultMapElements(context.evalNodes("/mapper/resultMap"));
sqlElement(context.evalNodes("/mapper/sql"));
buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {
throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
}
}注意下别名是在哪里配置的？
<select id="selectAll" type="User" resultType="Map"> // 别名就是在这里配置的
select * from test WHERE id =#{id}
</select>方法：解析参数别名等1：
private void parameterMapElement(List<XNode> list) {
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<>();
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);
// 方法：拿到别名方法1
Class<?> javaTypeClass = resolveClass(javaType);
//String --> varchar
JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
Class<? extends TypeHandler<?>> typeHandlerClass = resolveClass(typeHandler);
ParameterMapping parameterMapping = builderAssistant.buildParameterMapping(parameterClass, property, javaTypeClass, jdbcTypeEnum, resultMap, modeEnum, typeHandlerClass, numericScale);
parameterMappings.add(parameterMapping);
}
builderAssistant.addParameterMap(id, parameterClass, parameterMappings);
}
}方法：拿到别名方法1：
protected <T> Class<? extends T> resolveClass(String alias) {
if (alias == null) {
return null;
}
try {
return resolveAlias(alias);
} catch (Exception e) {
throw new BuilderException("Error resolving class. Cause: " + e, e);
}
}拿到别名方法一直点进去这个方法，这里就是在我们之前设置的现在取出来：
public <T> Class<T> resolveAlias(String string) {
try {
if (string == null) {
return null;
}
// issue #748
String key = string.toLowerCase(Locale.ENGLISH);
Class<T> value;
if (typeAliases.containsKey(key)) {
value = (Class<T>) typeAliases.get(key);
} else {
value = (Class<T>) Resources.classForName(string);
}
return value;
} catch (ClassNotFoundException e) {
throw new TypeException("Could not resolve type alias '" + string + "'. Cause: " + e, e);
}
}锚点1：真正放进去的是这句话：
buildStatementFromContext(context.evalNodes("select|insert|update|delete")); private void buildStatementFromContext(List<XNode> list) {
if (configuration.getDatabaseId() != null) {
buildStatementFromContext(list, configuration.getDatabaseId());
}
buildStatementFromContext(list, null);
}
private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
for (XNode context : list) {
final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
try {
//解析xml节点
statementParser.parseStatementNode();
} catch (IncompleteElementException e) {
//xml语句有问题时 存储到集合中 等解析完能解析的再重新解析
configuration.addIncompleteStatement(statementParser);
}
}
}这句话是这个意思：重新解析
锚点2:主要是这个代码：
//# $
public void parseStatementNode() {
String id = context.getStringAttribute("id");
String databaseId = context.getStringAttribute("databaseId");
if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
return;
}
String nodeName = context.getNode().getNodeName();
SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
//是否刷新缓存 默认值:增删改刷新 查询不刷新
boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
//是否使用二级缓存 默认值:查询使用 增删改不使用
boolean useCache = context.getBooleanAttribute("useCache", isSelect);
//是否需要处理嵌套查询结果 group by
// 三组数据 分成一个嵌套的查询结果
boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);
// Include Fragments before parsing
XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
//替换Includes标签为对应的sql标签里面的值
includeParser.applyIncludes(context.getNode());
String parameterType = context.getStringAttribute("parameterType");
Class<?> parameterTypeClass = resolveClass(parameterType);
//解析配置的自定义脚本语言驱动 mybatis plus
String lang = context.getStringAttribute("lang");
LanguageDriver langDriver = getLanguageDriver(lang);
// Parse selectKey after includes and remove them.
//解析selectKey
processSelectKeyNodes(id, parameterTypeClass, langDriver);
// Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
//设置主键自增规则
KeyGenerator keyGenerator;
String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;
keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);
if (configuration.hasKeyGenerator(keyStatementId)) {
keyGenerator = configuration.getKeyGenerator(keyStatementId);
} else {
keyGenerator = context.getBooleanAttribute("useGeneratedKeys",
configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))
? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
}
//解析Sql 根据sql文本来判断是否需要动态解析 如果没有动态sql语句且 只有#{}的时候 直接静态解析使用?占位 当有 ${} 不解析 留在后面去解析的
// 创建sql源方法1
SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
Integer fetchSize = context.getIntAttribute("fetchSize");
Integer timeout = context.getIntAttribute("timeout");
String parameterMap = context.getStringAttribute("parameterMap");
String resultType = context.getStringAttribute("resultType");
Class<?> resultTypeClass = resolveClass(resultType);
String resultMap = context.getStringAttribute("resultMap");
String resultSetType = context.getStringAttribute("resultSetType");
ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);
if (resultSetTypeEnum == null) {
resultSetTypeEnum = configuration.getDefaultResultSetType();
}
String keyProperty = context.getStringAttribute("keyProperty");
String keyColumn = context.getStringAttribute("keyColumn");
String resultSets = context.getStringAttribute("resultSets");
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
在这里判断是不是要动态的解析的。
创建sql源方法1：
public SqlSource parseScriptNode() {
//判断有没有 # $
MixedSqlNode rootSqlNode = parseDynamicTags(context);
SqlSource sqlSource;
if (isDynamic) {
//不解析
sqlSource = new DynamicSqlSource(configuration, rootSqlNode);
} else {
//用占位符方式来解析
sqlSource = new RawSqlSource(configuration, rootSqlNode, parameterType);
}
return sqlSource;
}进入这个方法：
protected MixedSqlNode parseDynamicTags(XNode node) {
List<SqlNode> contents = new ArrayList<>();
NodeList children = node.getNode().getChildNodes();
for (int i = 0; i < children.getLength(); i++) {
XNode child = node.newXNode(children.item(i));
if (child.getNode().getNodeType() == Node.CDATA_SECTION_NODE || child.getNode().getNodeType() == Node.TEXT_NODE) {
String data = child.getStringBody("");
// 在这里面解析的
TextSqlNode textSqlNode = new TextSqlNode(data);
if (textSqlNode.isDynamic()) {
contents.add(textSqlNode);
isDynamic = true;
} else {
contents.add(new StaticTextSqlNode(data));
}
} else if (child.getNode().getNodeType() == Node.ELEMENT_NODE) { // issue #628
String nodeName = child.getNode().getNodeName();
NodeHandler handler = nodeHandlerMap.get(nodeName);
if (handler == null) {
throw new BuilderException("Unknown element <" + nodeName + "> in SQL statement.");
}
handler.handleNode(child, contents);
isDynamic = true;
}
}
return new MixedSqlNode(contents);
}把#转化为？
public SqlSource parse(String originalSql, Class<?> parameterType, Map<String, Object> additionalParameters) {
ParameterMappingTokenHandler handler = new ParameterMappingTokenHandler(configuration, parameterType, additionalParameters);
GenericTokenParser parser = new GenericTokenParser("#{", "}", handler);
String sql = parser.parse(originalSql);
return new StaticSqlSource(configuration, sql, handler.getParameterMappings());
}public String parse(String text) {
if (text == null || text.isEmpty()) {
return "";
}
// search open token
int start = text.indexOf(openToken);
if (start == -1) {
return text;
}
char[] src = text.toCharArray();
int offset = 0;
final StringBuilder builder = new StringBuilder();
StringBuilder expression = null;
//遍历里面所有的#{} select ? ,#{id1} ${}
while (start > -1) {
if (start > 0 && src[start - 1] == '\\') {
// this open token is escaped. remove the backslash and continue.
builder.append(src, offset, start - offset - 1).append(openToken);
offset = start + openToken.length();
} else {
// found open token. let's search close token.
if (expression == null) {
expression = new StringBuilder();
} else {
expression.setLength(0);
}
builder.append(src, offset, start - offset);
offset = start + openToken.length();
int end = text.indexOf(closeToken, offset);
while (end > -1) {
if (end > offset && src[end - 1] == '\\') {
// this close token is escaped. remove the backslash and continue.
expression.append(src, offset, end - offset - 1).append(closeToken);
offset = end + closeToken.length();
end = text.indexOf(closeToken, offset);
} else {
expression.append(src, offset, end - offset);
break;
}
}
if (end == -1) {
// close token was not found.
builder.append(src, start, src.length - start);
offset = src.length;
} else {
builder.append(handler.handleToken(expression.toString()));
offset = end + closeToken.length();
}
}
start = text.indexOf(openToken, offset);
}
if (offset < src.length) {
builder.append(src, offset, src.length - offset);
}
return builder.toString();
}
} //目前为止只是在解析xml
//全局扫描#{id} 字符串之后 会把里面所有 #{} 调用handleToken 替换为?
@Override
public String handleToken(String content) {
parameterMappings.add(buildParameterMapping(content));
return "?";
}----------------下半节课
public boolean isDynamic() {
DynamicCheckerTokenParser checker = new DynamicCheckerTokenParser();
GenericTokenParser parser = createParser(checker);
parser.parse(text);
return checker.isDynamic();
}看到有$符号的节点就是Dynamic的就置为true。
//PreparedStatement 一个是预编译 一个不是预编译 Statement
//当扫描到${}的时候调用此方法 其实就是不解析 在运行时候在替换成具体的值
@Override
public String handleToken(String content) {
this.isDynamic = true;
return null;
}$符号的解析器具：
#的解析器：
关键点：锚点2:
所有解析完毕之后则：
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);锚点3:
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
// 方法：在这里面解析xml文件1
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
//绑定Namespace里面的Class对象
bindMapperForNamespace();
}
//重新解析之前解析不了的节点
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
} //解析Mapper对象
public void parse() {
String resource = type.toString();
//如果之前解析了xml 这里就不会在解析了
if (!configuration.isResourceLoaded(resource)) {
loadXmlResource();
configuration.addLoadedResource(resource);
assistant.setCurrentNamespace(type.getName());
parseCache();
parseCacheRef();
Method[] methods = type.getMethods();
for (Method method : methods) {
try {
// issue #237
if (!method.isBridge()) {
parseStatement(method);
}
} catch (IncompleteElementException e) {
configuration.addIncompleteMethod(new MethodResolver(this, method));
}
}
}
parsePendingMethods();
} private void loadXmlResource() {
// Spring may not know the real resource name so we check a flag
// to prevent loading again a resource twice
// this flag is set at XMLMapperBuilder#bindMapperForNamespace
if (!configuration.isResourceLoaded("namespace:" + type.getName())) {
String xmlResource = type.getName().replace('.', '/') + ".xml";
// #1347
InputStream inputStream = type.getResourceAsStream("/" + xmlResource);
if (inputStream == null) {
// Search XML mapper that is not in the module but in the classpath.
try {
inputStream = Resources.getResourceAsStream(type.getClassLoader(), xmlResource);
} catch (IOException e2) {
// ignore, resource is not required
}
}
if (inputStream != null) {
XMLMapperBuilder xmlParser = new XMLMapperBuilder(inputStream, assistant.getConfiguration(), xmlResource, configuration.getSqlFragments(), type.getName());
xmlParser.parse();
}
}
}
private SqlCommandType getSqlCommandType(Method method) {
Class<? extends Annotation> type = getSqlAnnotationType(method);
if (type == null) {
type = getSqlProviderAnnotationType(method);
if (type == null) {
return SqlCommandType.UNKNOWN;
}
if (type == SelectProvider.class) {
type = Select.class;
} else if (type == InsertProvider.class) {
type = Insert.class;
} else if (type == UpdateProvider.class) {
type = Update.class;
} else if (type == DeleteProvider.class) {
type = Delete.class;
}
}
return SqlCommandType.valueOf(type.getSimpleName().toUpperCase(Locale.ENGLISH));
}注解的。
