Mybatis source code
声明：此过程仅记录本人DEBUG过程，如有错误请指出！
JDBC
Example:
public class JDBCTest {
12
13 public static void jdbcDemoSelect(String driver,String url,String user,String password) throws Exception {
14
15 //1.加载类驱动
16 Class.forName(driver);
17 Connection con = DriverManager.getConnection(url,user,password);
18
19 // if(!con.isClosed())
20 // System.out.println("succeeded connection to the database");
21
22 //2.创建statement类对象，用来执行SQL语句
23 Statement statement = con.createStatement();
24
25 //SQL语句
26 String sql = "select * from emp";
27
28 //3.ResultSet类，用来存放获取的结果集
29 ResultSet set = statement.executeQuery(sql);
30
31 String eid=null,ename=null,price=null;
32
33 while(set.next()) {
34 eid = set.getString("eid");
35 ename = set.getString("ename");
36 price = set.getString("price");
37
38 System.out.println(eid+"\t"+ename+"\t"+price);
39 }
40
41 }
Get the driver here
Mybatis source code follow-up
Take the build method as the entrance
Enter the parse method
Enter the parseConfiguration method
Corresponding mybatis.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>
<settings>
<setting name="logImpl" value="LOG4J"/>
</settings>
<!-- 别名 -->
<typeAliases>
<!-- <typeAlias type="com.test.pojo.People" alias="po" /> -->
<package name="com.lmy.pojo" />
</typeAliases>
<environments default="default">
<environment id="default">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/usermanager?autoReconnect=true&useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="121891"/>
</dataSource>
</environment>
</environments>
<mappers>
<!-- <mapper resource="com/test/mapper/StudentMapper.xml" />
<mapper resource="com/test/mapper/TeacherMapper.xml" /> -->
<!--<mapper class="com.test.mapper.TeacherMapper" />-->
<package name="com.lmy.mapper"/>
</mappers>
</configuration>
Enter the mapperElement method
Suppose we configure pachage in xml
Suppose we configure the resource of mapper in xml
Enter the configurationElement method
Enter the parseStatementNode method, here to get some information about the node, including some attributes
public void parseStatementNode() {
String id = context.getStringAttribute("id");
String databaseId = context.getStringAttribute("databaseId");
if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) return;
Integer fetchSize = context.getIntAttribute("fetchSize");
Integer timeout = context.getIntAttribute("timeout");
String parameterMap = context.getStringAttribute("parameterMap");
String parameterType = context.getStringAttribute("parameterType");
Class<?> parameterTypeClass = resolveClass(parameterType);
String resultMap = context.getStringAttribute("resultMap");
String resultType = context.getStringAttribute("resultType");
String lang = context.getStringAttribute("lang");
LanguageDriver langDriver = getLanguageDriver(lang);
Class<?> resultTypeClass = resolveClass(resultType);
String resultSetType = context.getStringAttribute("resultSetType");
StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);
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());
// Parse selectKey after includes and remove them.
processSelectKeyNodes(id, parameterTypeClass, langDriver);
// Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
String resultSets = context.getStringAttribute("resultSets");
String keyProperty = context.getStringAttribute("keyProperty");
String keyColumn = context.getStringAttribute("keyColumn");
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))
? new Jdbc3KeyGenerator() : new NoKeyGenerator();
}
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
Finally construct a MappedStatement
Enter the addMappedStatement method
public MappedStatement addMappedStatement(
String id,
SqlSource sqlSource,
StatementType statementType,
SqlCommandType sqlCommandType,
Integer fetchSize,
Integer timeout,
String parameterMap,
Class<?> parameterType,
String resultMap,
Class<?> resultType,
ResultSetType resultSetType,
boolean flushCache,
boolean useCache,
boolean resultOrdered,
KeyGenerator keyGenerator,
String keyProperty,
String keyColumn,
String databaseId,
LanguageDriver lang,
String resultSets) {
if (unresolvedCacheRef) throw new IncompleteElementException("Cache-ref not yet resolved");
id = applyCurrentNamespace(id, false);
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
MappedStatement.Builder statementBuilder = new MappedStatement.Builder(configuration, id, sqlSource, sqlCommandType);
statementBuilder.resource(resource);
statementBuilder.fetchSize(fetchSize);
statementBuilder.statementType(statementType);
statementBuilder.keyGenerator(keyGenerator);
statementBuilder.keyProperty(keyProperty);
statementBuilder.keyColumn(keyColumn);
statementBuilder.databaseId(databaseId);
statementBuilder.lang(lang);
statementBuilder.resultOrdered(resultOrdered);
statementBuilder.resulSets(resultSets);
setStatementTimeout(timeout, statementBuilder);
setStatementParameterMap(parameterMap, parameterType, statementBuilder);
setStatementResultMap(resultMap, resultType, resultSetType, statementBuilder);
setStatementCache(isSelect, flushCache, useCache, currentCache, statementBuilder);
MappedStatement statement = statementBuilder.build();
configuration.addMappedStatement(statement);
return statement;
}
Here we can see the final encapsulated MappedStatement object is added to a collection
This is a mapper collection
Everyone knows that if the keys of the Map collection are the same, it will be overwritten, but if we configure the methods in the same mapper in multiple minutes, an error will be reported. The reason is the put method, which is rewritten here.
Analyze and execute SQL
Enter getMapper
It inherits the InvocationHandler interface
So let’s take a look at his invoke method
Enter this execute method
Processing according to sql
I use select here, first determine the type of return value, here is a list collection, so there are multiple
The configuration is as follows
Since we are using #{} as static SQL, the SQL here still uses placeholders? , Later assigned by set
Set the value here