目录
- [1. 使用](#1. 使用)
- [1.1. 新建maven项目](#1.1. 新建maven项目)
- [1.2. pom.xml](#1.2. pom.xml)
- [1.3. 配置mybatis](#1.3. 配置mybatis)
- [1.4. 新建mapper](#1.4. 新建mapper)
- [1.5. 测试](#1.5. 测试)
- [1.6. 项目结构](#1.6. 项目结构)
- [2. 源码分析](#2. 源码分析)
- [2.1. 框架分层](#2.1. 框架分层)
- [2.2. 四大对象](#2.2. 四大对象)
- [2.3. 要分析的代码](#2.3. 要分析的代码)
- [2.4. 获取SqlSessionFactory对象](#2.4. 获取SqlSessionFactory对象)
- [2.4.1. 解析xml配置](#2.4.1. 解析xml配置)
- [2.4.1.1. 解析mybatis全局配置](#2.4.1.1. 解析mybatis全局配置)
- [2.4.1.2. 解析mapper.xml](#2.4.1.2. 解析mapper.xml)
- [2.4.1. 解析xml配置](#2.4.1. 解析xml配置)
- [2.5. 获取sqlsession对象](#2.5. 获取sqlsession对象)
- [2.5.1. 获取数据库链接信息](#2.5.1. 获取数据库链接信息)
- [2.5.2. 创建事务管理工厂](#2.5.2. 创建事务管理工厂)
- [2.5.3. 创建Executor](#2.5.3. 创建Executor)
- [2.5.3.1. Executor继承体系](#2.5.3.1. Executor继承体系)
- [2.6. 获取mapper类的代理对象](#2.6. 获取mapper类的代理对象)
- [2.6.1. 从MapperRegistry通过mapper名获取MapperProxyFactory](#2.6.1. 从MapperRegistry通过mapper名获取MapperProxyFactory)
- [2.6.2. 通过MapperProxyFactory使用jdk动态代理创建mapper](#2.6.2. 通过MapperProxyFactory使用jdk动态代理创建mapper)
- [2.7. 通过代理对象执行CRUD方法](#2.7. 通过代理对象执行CRUD方法)
- [2.7.1. 通过MapperMethod执行sql](#2.7.1. 通过MapperMethod执行sql)
- [2.7.2. 怎么执行sql的](#2.7.2. 怎么执行sql的)
- [2.7.2.1. 把sql语句封装成MappedStatement](#2.7.2.1. 把sql语句封装成MappedStatement)
- [2.7.2.2. 通过Executor执行sql](#2.7.2.2. 通过Executor执行sql)
- [2.7.2.2.1. 二级缓存中有则直接返回](#2.7.2.2.1. 二级缓存中有则直接返回)
- [2.7.2.2.2. 一级缓存中有则直接返回,没有在查数据库](#2.7.2.2.2. 一级缓存中有则直接返回,没有在查数据库)
- [2.7.2.2.3. 真正的jdbc操作](#2.7.2.2.3. 真正的jdbc操作)
- [3. 参考](#3. 参考)
1. 使用
1.1. 新建maven项目
1.2. pom.xml
xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.zsk</groupId>
<artifactId>mybatis_test</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.version>1.8</java.version>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.3</version>
</dependency>
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>42.2.8</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
</plugin>
</plugins>
<!--配置资源目录-->
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.*</include>
</includes>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.*</include>
</includes>
</resource>
<!-- 打包时将jsp文件拷贝到META-INF目录下 -->
<resource>
<!-- 指定resources插件处理哪个目录下的资源文件 -->
<directory>src/main/webapp</directory>
<!--注意此次必须要放在此目录下才能被访问到 -->
<targetPath>META-INF/resources</targetPath>
<includes>
<include>**/*.*</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
</build>
</project>
1.3. 配置mybatis
- resources/jdbc.properties
properties
driver=org.postgresql.Driver
url=jdbc:postgresql://localhost:5432/tao
username=zsk
password=zskroot
- resources/mybatis-config.xml
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>
<properties resource='jdbc.properties'/>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="mapper/UserMapper.xml"/>
</mappers>
</configuration>
1.4. 新建mapper
- com.zsk.model.User
java
package com.zsk.model;
/**
* @description:
* @author: zsk
* @create: 2019-11-30 15:32
**/
public class User
{
private Long id;
private String username;
public Long getId()
{
return id;
}
public void setId(Long id)
{
this.id = id;
}
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
@Override
public String toString()
{
return "User{" + "id=" + id + ", username='" + username + '\'' + '}';
}
}
- com.zsk.dao.UserMapper
java
package com.zsk.dao;
import com.zsk.model.User;
/**
* @description:
* @author: zsk
* @create: 2019-11-30 15:31
**/
public interface UserMapper
{
User getById(Long id);
}
- mapper/UserMapper.xml
xml
<?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.zsk.dao.UserMapper">
<select id="getById" resultType="com.zsk.model.User" parameterType="java.lang.Long">
select * from tb_user where id = #{id}
</select>
</mapper>
1.5. 测试
- Main
java
import com.zsk.dao.UserMapper;
import com.zsk.model.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
/**
* @description:
* @author: zsk
* @create: 2019-11-30 15:28
**/
public class Main
{
public static void main(String[] args) throws IOException
{
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
try (SqlSession session = sqlSessionFactory.openSession())
{
UserMapper mapper = session.getMapper(UserMapper.class);
User user = mapper.getById(7L);
System.out.println(user);
}
}
}
1.6. 项目结构
2. 源码分析
目录
- [1. 使用](#1. 使用)
- [1.1. 新建maven项目](#1.1. 新建maven项目)
- [1.2. pom.xml](#1.2. pom.xml)
- [1.3. 配置mybatis](#1.3. 配置mybatis)
- [1.4. 新建mapper](#1.4. 新建mapper)
- [1.5. 测试](#1.5. 测试)
- [1.6. 项目结构](#1.6. 项目结构)
- [2. 源码分析](#2. 源码分析)
- [2.1. 框架分层](#2.1. 框架分层)
- [2.2. 四大对象](#2.2. 四大对象)
- [2.3. 要分析的代码](#2.3. 要分析的代码)
- [2.4. 获取SqlSessionFactory对象](#2.4. 获取SqlSessionFactory对象)
- [2.4.1. 解析xml配置](#2.4.1. 解析xml配置)
- [2.4.1.1. 解析mybatis全局配置](#2.4.1.1. 解析mybatis全局配置)
- [2.4.1.2. 解析mapper.xml](#2.4.1.2. 解析mapper.xml)
- [2.4.1. 解析xml配置](#2.4.1. 解析xml配置)
- [2.5. 获取sqlsession对象](#2.5. 获取sqlsession对象)
- [2.5.1. 获取数据库链接信息](#2.5.1. 获取数据库链接信息)
- [2.5.2. 创建事务管理工厂](#2.5.2. 创建事务管理工厂)
- [2.5.3. 创建Executor](#2.5.3. 创建Executor)
- [2.5.3.1. Executor继承体系](#2.5.3.1. Executor继承体系)
- [2.6. 获取mapper类的代理对象](#2.6. 获取mapper类的代理对象)
- [2.6.1. 从MapperRegistry通过mapper名获取MapperProxyFactory](#2.6.1. 从MapperRegistry通过mapper名获取MapperProxyFactory)
- [2.6.2. 通过MapperProxyFactory使用jdk动态代理创建mapper](#2.6.2. 通过MapperProxyFactory使用jdk动态代理创建mapper)
- [2.7. 通过代理对象执行CRUD方法](#2.7. 通过代理对象执行CRUD方法)
- [2.7.1. 通过MapperMethod执行sql](#2.7.1. 通过MapperMethod执行sql)
- [2.7.2. 怎么执行sql的](#2.7.2. 怎么执行sql的)
- [2.7.2.1. 把sql语句封装成MappedStatement](#2.7.2.1. 把sql语句封装成MappedStatement)
- [2.7.2.2. 通过Executor执行sql](#2.7.2.2. 通过Executor执行sql)
- [2.7.2.2.1. 二级缓存中有则直接返回](#2.7.2.2.1. 二级缓存中有则直接返回)
- [2.7.2.2.2. 一级缓存中有则直接返回,没有在查数据库](#2.7.2.2.2. 一级缓存中有则直接返回,没有在查数据库)
- [2.7.2.2.3. 真正的jdbc操作](#2.7.2.2.3. 真正的jdbc操作)
- [3. 参考](#3. 参考)
2.1. 框架分层
2.2. 四大对象
MyBatis创建四大对象的时候,使用动态代理机制添加了拦截器.
- Executor
- ParameterHandler
- ResultSetHandler
- StatementHandler
2.3. 要分析的代码
java
public class Test
{
public static void main(String[] args) throws Exception
{
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
//1.获取SqlSessionFactory对象
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//2.获取sqlsession对象
SqlSession session = sqlSessionFactory.openSession();
//3.获取接口的代理对象
TtestMapper mapper = session.getMapper(TtestMapper.class);
//4.执行CRUD方法
Ttest blog = mapper.getOne(1);
System.out.println(blog);
session.close();
}
}
2.4. 获取SqlSessionFactory对象
- new SqlSessionFactoryBuilder().build(inputStream)
java
public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
try {
//读取mybatis-config.xml,并把配置信息封装到XMLConfigBuilder
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
//把xml文件中的配置全部封装到Configuraion里面
return build(parser.parse());
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error building SqlSession.", e);
} finally {
ErrorContext.instance().reset();
try {
inputStream.close();
} catch (IOException e) {
// Intentionally ignore. Prefer previous error.
}
}
}
2.4.1. 解析xml配置
2.4.1.1. 解析mybatis全局配置
- XMLConfigBuilder
java
public Configuration parse() {
//解析过了直接抛出异常
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
//通过XPath获取mybatis-config.xml中的configuration节点作为root节点,继续解析下级节点
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
private void parseConfiguration(XNode root) {
try {
//issue #117 read properties first
propertiesElement(root.evalNode("properties"));
//获取settings节点,封装到Properties中
Properties settings = settingsAsProperties(root.evalNode("settings"));
loadCustomVfs(settings);
loadCustomLogImpl(settings);
typeAliasesElement(root.evalNode("typeAliases"));
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
//把settings节点下的所有属性设置到Configuration中
settingsElement(settings);
// read it after objectFactory and objectWrapperFactory issue #631
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
//解析mappers标签
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
private void settingsElement(Properties props) {
//没有的话设置的默认值
configuration.setAutoMappingBehavior(AutoMappingBehavior.valueOf(props.getProperty("autoMappingBehavior", "PARTIAL")));
configuration.setAutoMappingUnknownColumnBehavior(AutoMappingUnknownColumnBehavior.valueOf(props.getProperty("autoMappingUnknownColumnBehavior", "NONE")));
configuration.setCacheEnabled(booleanValueOf(props.getProperty("cacheEnabled"), true));
configuration.setProxyFactory((ProxyFactory) createInstance(props.getProperty("proxyFactory")));
configuration.setLazyLoadingEnabled(booleanValueOf(props.getProperty("lazyLoadingEnabled"), false));
configuration.setAggressiveLazyLoading(booleanValueOf(props.getProperty("aggressiveLazyLoading"), false));
configuration.setMultipleResultSetsEnabled(booleanValueOf(props.getProperty("multipleResultSetsEnabled"), true));
configuration.setUseColumnLabel(booleanValueOf(props.getProperty("useColumnLabel"), true));
configuration.setUseGeneratedKeys(booleanValueOf(props.getProperty("useGeneratedKeys"), false));
configuration.setDefaultExecutorType(ExecutorType.valueOf(props.getProperty("defaultExecutorType", "SIMPLE")));
configuration.setDefaultStatementTimeout(integerValueOf(props.getProperty("defaultStatementTimeout"), null));
configuration.setDefaultFetchSize(integerValueOf(props.getProperty("defaultFetchSize"), null));
configuration.setMapUnderscoreToCamelCase(booleanValueOf(props.getProperty("mapUnderscoreToCamelCase"), false));
configuration.setSafeRowBoundsEnabled(booleanValueOf(props.getProperty("safeRowBoundsEnabled"), false));
configuration.setLocalCacheScope(LocalCacheScope.valueOf(props.getProperty("localCacheScope", "SESSION")));
configuration.setJdbcTypeForNull(JdbcType.valueOf(props.getProperty("jdbcTypeForNull", "OTHER")));
configuration.setLazyLoadTriggerMethods(stringSetValueOf(props.getProperty("lazyLoadTriggerMethods"), "equals,clone,hashCode,toString"));
configuration.setSafeResultHandlerEnabled(booleanValueOf(props.getProperty("safeResultHandlerEnabled"), true));
configuration.setDefaultScriptingLanguage(resolveClass(props.getProperty("defaultScriptingLanguage")));
configuration.setDefaultEnumTypeHandler(resolveClass(props.getProperty("defaultEnumTypeHandler")));
configuration.setCallSettersOnNulls(booleanValueOf(props.getProperty("callSettersOnNulls"), false));
configuration.setUseActualParamName(booleanValueOf(props.getProperty("useActualParamName"), true));
configuration.setReturnInstanceForEmptyRow(booleanValueOf(props.getProperty("returnInstanceForEmptyRow"), false));
configuration.setLogPrefix(props.getProperty("logPrefix"));
configuration.setConfigurationFactory(resolveClass(props.getProperty("configurationFactory")));
}
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
//有package节点则走下面的逻辑
if ("package".equals(child.getName())) {
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);
} else {
//根据resource,url,class节点确定走那段逻辑
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);
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
//解析mapper标签
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());
mapperParser.parse();
} else if (resource == null && url == null && mapperClass != null) {
//<mapper class="com.zsk.test.mapper.TtestMapper"></mapper>
//创建class对象加载到configuration中
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.");
}
}
}
}
}
2.4.1.2. 解析mapper.xml
- XMLMapperBuilder
java
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
//mapper标签
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}
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"));
//解析parameterMap,resultMap,sql标签并存放到Configuration中
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
resultMapElements(context.evalNodes("/mapper/resultMap"));
sqlElement(context.evalNodes("/mapper/sql"));
//解析CRUD标签
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);
}
}
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 {
statementParser.parseStatementNode();
} catch (IncompleteElementException e) {
configuration.addIncompleteStatement(statementParser);
}
}
}
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;
boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
boolean useCache = context.getBooleanAttribute("useCache", isSelect);
boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);
// Include Fragments before parsing
XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
includeParser.applyIncludes(context.getNode());
String parameterType = context.getStringAttribute("parameterType");
Class<?> parameterTypeClass = resolveClass(parameterType);
String lang = context.getStringAttribute("lang");
LanguageDriver langDriver = getLanguageDriver(lang);
// Parse selectKey after includes and remove them.
processSelectKeyNodes(id, parameterTypeClass, langDriver);
// Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
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;
}
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);
String keyProperty = context.getStringAttribute("keyProperty");
String keyColumn = context.getStringAttribute("keyColumn");
String resultSets = context.getStringAttribute("resultSets");
//最终封装成MappedStatement对象
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
2.5. 获取sqlsession对象
- DefaultSqlSessionFactory.openSession()
java
public class DefaultSqlSessionFactory implements SqlSessionFactory {
@Override
public SqlSession openSession() {
//根据Configuration配置的ExecutorType(默认是SIMPLE)来获取SqlSession
return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, false);
}
private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
Transaction tx = null;
try {
//从Configuration中获取数据库链接信息
final Environment environment = configuration.getEnvironment();
//创建事务
final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
//创建执行器
final Executor executor = configuration.newExecutor(tx, execType);
//最后返回的SqlSession包含了Configuration,Executor信息
return new DefaultSqlSession(configuration, executor, autoCommit);
} catch (Exception e) {
closeTransaction(tx); // may have fetched a connection so lets call close()
throw ExceptionFactory.wrapException("Error opening session. Cause: " + e, e);
} finally {
ErrorContext.instance().reset();
}
}
}
2.5.1. 获取数据库链接信息
2.5.2. 创建事务管理工厂
2.5.3. 创建Executor
- Configuration
java
public class Configuration {
public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
//默认是ExecutorType.SIMPLE
executorType = executorType == null ? defaultExecutorType : executorType;
executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
Executor executor;
//根据不同的type创建不同的Executor
if (ExecutorType.BATCH == executorType) {
executor = new BatchExecutor(this, transaction);
} else if (ExecutorType.REUSE == executorType) {
executor = new ReuseExecutor(this, transaction);
} else {
executor = new SimpleExecutor(this, transaction);
}
//装饰器模式:把原始的Executor用Cache包装
if (cacheEnabled) {
executor = new CachingExecutor(executor);
}
//也是装饰器模式?--把所有插件都包装到Executor上
executor = (Executor) interceptorChain.pluginAll(executor);
return executor;
}
}
2.5.3.1. Executor继承体系
2.6. 获取mapper类的代理对象
- DefaultSqlSession.getMapper(TtestMapper.class)
java
@Override
public <T> T getMapper(Class<T> type) {
//调用Configuration的getMapper方法
return configuration.getMapper(type, this);
}
2.6.1. 从MapperRegistry通过mapper名获取MapperProxyFactory
- Configuration
java
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
//调用MapperRegistry(存储了Mapper名:MapperProxyFactory)的getMapper方法
return mapperRegistry.getMapper(type, sqlSession);
}
- MapperRegistry
java
@SuppressWarnings("unchecked")
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
//从Map<Class<?>, MapperProxyFactory<?>> knownMappers = new HashMap<>();获取MapperProxyFactory
final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
//没找到则抛出异常
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}
2.6.2. 通过MapperProxyFactory使用jdk动态代理创建mapper
- MapperProxyFactory
java
public T newInstance(SqlSession sqlSession) {
//class MapperProxy<T> implements InvocationHandler,JDK的动态代理接口
final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
@SuppressWarnings("unchecked")
protected T newInstance(MapperProxy<T> mapperProxy) {
//参数:被代理对象的类加载器,被代理对象实现的接口,对立对象实例
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}
2.7. 通过代理对象执行CRUD方法
- MapperProxy.getOne(1)
java
//调用的是代理类的invoke方法
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
//如果这个方法是Object类的方法,那么直接调用
if (Object.class.equals(method.getDeclaringClass())) {
return method.invoke(this, args);
//判断是否接口的方法
} else if (isDefaultMethod(method)) {
return invokeDefaultMethod(proxy, method, args);
}
} catch (Throwable t) {
throw ExceptionUtil.unwrapThrowable(t);
}
//从缓存中获取MapperMethod
final MapperMethod mapperMethod = cachedMapperMethod(method);
//执行sql语句
return mapperMethod.execute(sqlSession, args);
}
private MapperMethod cachedMapperMethod(Method method) {
//Map中有这个方法的话直接返回,没有则new返回
return methodCache.computeIfAbsent(method, k -> new MapperMethod(mapperInterface, method, sqlSession.getConfiguration()));
}
2.7.1. 通过MapperMethod执行sql
- MapperMethod
java
public class MapperMethod {
private final SqlCommand command;
private final MethodSignature method;
public MapperMethod(Class<?> mapperInterface, Method method, Configuration config) {
//封装sql语句
this.command = new SqlCommand(config, mapperInterface, method);
//封装sql语句的参数
this.method = new MethodSignature(config, mapperInterface, method);
}
public Object execute(SqlSession sqlSession, Object[] args) {
Object result;
//根据sql语句的类型调用CRUD
switch (command.getType()) {
case INSERT: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.insert(command.getName(), param));
break;
}
case UPDATE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.update(command.getName(), param));
break;
}
case DELETE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.delete(command.getName(), param));
break;
}
case SELECT:
//没有返回值
if (method.returnsVoid() && method.hasResultHandler()) {
executeWithResultHandler(sqlSession, args);
result = null;
//返回多个
} else if (method.returnsMany()) {
result = executeForMany(sqlSession, args);
//返回ma
} else if (method.returnsMap()) {
result = executeForMap(sqlSession, args);
//返回游标--分页?
} else if (method.returnsCursor()) {
result = executeForCursor(sqlSession, args);
//返回一个
} else {
Object param = method.convertArgsToSqlCommandParam(args);
//调用SqlSession的selectOne
result = sqlSession.selectOne(command.getName(), param);
if (method.returnsOptional()
&& (result == null || !method.getReturnType().equals(result.getClass()))) {
result = Optional.ofNullable(result);
}
}
break;
case FLUSH:
result = sqlSession.flushStatements();
break;
default:
throw new BindingException("Unknown execution method for: " + command.getName());
}
if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
throw new BindingException("Mapper method '" + command.getName()
+ " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
}
return result;
}
}
2.7.2. 怎么执行sql的
- DefaultSqlSession
java
@Override
public <T> T selectOne(String statement, Object parameter) {
// Popular vote was to return null on 0 results and throw exception on too many.
//都是调用的list方法
List<T> list = this.selectList(statement, parameter);
//一个的话直接返回
if (list.size() == 1) {
return list.get(0);
//多个的话有问题,抛出异常
} else if (list.size() > 1) {
throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
//一个都没有返回null
} else {
return null;
}
}
@Override
public <E> List<E> selectList(String statement, Object parameter) {
return this.selectList(statement, parameter, RowBounds.DEFAULT);
}
@Override
public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
try {
//调用Configuration把sql和参数封装成MapperStatement
MappedStatement ms = configuration.getMappedStatement(statement);
//通过执行器来执行
return executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
} finally {
ErrorContext.instance().reset();
}
}
2.7.2.1. 把sql语句封装成MappedStatement
- Configuration
java
public MappedStatement getMappedStatement(String id) {
return this.getMappedStatement(id, true);
}
public MappedStatement getMappedStatement(String id, boolean validateIncompleteStatements) {
//没有生成过这条语句则重新构建在放入map
if (validateIncompleteStatements) {
buildAllStatements();
}
//从map中取出这条语句,防止反复解析
return mappedStatements.get(id);
}
2.7.2.2. 通过Executor执行sql
2.7.2.2.1. 二级缓存中有则直接返回
- CachingExecutor
java
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
//取出sql
BoundSql boundSql = ms.getBoundSql(parameterObject);
//构造缓存的key
CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
throws SQLException {
Cache cache = ms.getCache();
//缓存中有
if (cache != null) {
flushCacheIfRequired(ms);
if (ms.isUseCache() && resultHandler == null) {
ensureNoOutParams(ms, boundSql);
@SuppressWarnings("unchecked")
//从缓存中取
List<E> list = (List<E>) tcm.getObject(cache, key);
//取出的为空
if (list == null) {
//重新执行sql,再次放入缓存
list = delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
tcm.putObject(cache, key, list); // issue #578 and #116
}
return list;
}
}
//BaseExecutor的query方法
return delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
2.7.2.2.2. 一级缓存中有则直接返回,没有在查数据库
- BaseExecutor
java
@SuppressWarnings("unchecked")
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
if (closed) {
throw new ExecutorException("Executor was closed.");
}
if (queryStack == 0 && ms.isFlushCacheRequired()) {
clearLocalCache();
}
List<E> list;
try {
queryStack++;
//一级缓存?
list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
if (list != null) {
handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
} else {
//从数据库中查
list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
} finally {
queryStack--;
}
if (queryStack == 0) {
for (DeferredLoad deferredLoad : deferredLoads) {
deferredLoad.load();
}
// issue #601
deferredLoads.clear();
if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
// issue #482
clearLocalCache();
}
}
return list;
}
private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
List<E> list;
localCache.putObject(key, EXECUTION_PLACEHOLDER);
try {
//SimpleExecutor
list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
} finally {
localCache.removeObject(key);
}
localCache.putObject(key, list);
if (ms.getStatementType() == StatementType.CALLABLE) {
localOutputParameterCache.putObject(key, parameter);
}
return list;
}
2.7.2.2.3. 真正的jdbc操作
- SimpleExecutor
java
@Override
public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
Statement stmt = null;
try {
Configuration configuration = ms.getConfiguration();
StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
//JDBC操作
stmt = prepareStatement(handler, ms.getStatementLog());
return handler.query(stmt, resultHandler);
} finally {
closeStatement(stmt);
}
}