一.工程目录
在这里插入图片描述
1.Configuration 主要是mybatis的配置
@Data
public class Configuration {
protected Connection connection;
protected Map dataSource;
protected Map mapperElement;
}
2.SqlSessionFactory 构建SqlSession的工厂，用于创建SqlSession
public class DefaultSqlSessionFactory implements SqlSessionFactory {
private final Configuration configuration;
public DefaultSqlSessionFactory(Configuration configuration) {
this.configuration = configuration;
}
@Override
public SqlSession openSession() {
return new DefaultSqlSession(configuration.connection, configuration.mapperElement);
}
}
3.SqlSession 用于执行sql的类
public interface SqlSession {
T selectOne(String statement);
T selectOne(String statement, Object parameter) throws Exception;
List selectList(String statement);
List selectList(String statement, Object parameter);
void close();
}
public class DefaultSqlSession implements SqlSession {
private Connection connection;
private Map mapperElement;
public DefaultSqlSession(Connection connection, Map mapperElement) {
this.connection = connection;
this.mapperElement = mapperElement;
}
@Override
public T selectOne(String statement) {
try {
XNode xNode = mapperElement.get(statement);
PreparedStatement preparedStatement = connection.prepareStatement(xNode.getSql());
ResultSet resultSet = preparedStatement.executeQuery();
List objects = resultSet2Obj(resultSet, Class.forName(xNode.getResultType()));
return objects.get(0);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
public T selectOne(String statement, Object parameter) throws Exception {
XNode xNode = mapperElement.get(statement);
// 根据命名空间和方法名 获取sql脚本
if (xNode == null){
throw new Exception("命名空间错误或方法不存在");
}
Map parameterMap = xNode.getParameter();
try {
PreparedStatement preparedStatement = connection.prepareStatement(xNode.getSql());
buildParameter(preparedStatement, parameter, parameterMap);
ResultSet resultSet = preparedStatement.executeQuery();
List objects = resultSet2Obj(resultSet, Class.forName(xNode.getResultType()));
return objects.get(0);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
public List selectList(String statement) {
XNode xNode = mapperElement.get(statement);
try {
PreparedStatement preparedStatement = connection.prepareStatement(xNode.getSql());
ResultSet resultSet = preparedStatement.executeQuery();
return resultSet2Obj(resultSet, Class.forName(xNode.getResultType()));
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
public List selectList(String statement, Object parameter) {
XNode xNode = mapperElement.get(statement);
Map parameterMap = xNode.getParameter();
try {
PreparedStatement preparedStatement = connection.prepareStatement(xNode.getSql());
buildParameter(preparedStatement, parameter, parameterMap);
ResultSet resultSet = preparedStatement.executeQuery();
return resultSet2Obj(resultSet, Class.forName(xNode.getResultType()));
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
private void buildParameter(PreparedStatement preparedStatement, Object parameter, Map parameterMap) throws SQLException, IllegalAccessException {
int size = parameterMap.size();
// 单个参数
if (parameter instanceof Long) {
for (int i = 1; i <= size; i++) {
preparedStatement.setLong(i, Long.parseLong(parameter.toString()));
}
return;
}
if (parameter instanceof Integer) {
for (int i = 1; i <= size; i++) {
preparedStatement.setInt(i, Integer.parseInt(parameter.toString()));
}
return;
}
if (parameter instanceof String) {
for (int i = 1; i <= size; i++) {
preparedStatement.setString(i, parameter.toString());
}
return;
}
Map fieldMap = new HashMap<>();
// 对象参数
Field[] declaredFields = parameter.getClass().getDeclaredFields();
for (Field field : declaredFields) {
String name = field.getName();
field.setAccessible(true);
Object obj = field.get(parameter);
field.setAccessible(false);
fieldMap.put(name, obj);
}
for (int i = 1; i <= size; i++) {
String parameterDefine = parameterMap.get(i);
Object obj = fieldMap.get(parameterDefine);
if (obj instanceof Short) {
preparedStatement.setShort(i, Short.parseShort(obj.toString()));
continue;
}
if (obj instanceof Integer) {
preparedStatement.setInt(i, Integer.parseInt(obj.toString()));
continue;
}
if (obj instanceof Long) {
preparedStatement.setLong(i, Long.parseLong(obj.toString()));
continue;
}
if (obj instanceof String) {
preparedStatement.setString(i, obj.toString());
continue;
}
if (obj instanceof Date) {
preparedStatement.setDate(i, (java.sql.Date) obj);
}
}
}
private List resultSet2Obj(ResultSet resultSet, Class clazz) {
List list = new ArrayList<>();
try {
ResultSetMetaData metaData = resultSet.getMetaData();
int columnCount = metaData.getColumnCount();
// 每次遍历行值
while (resultSet.next()) {
T obj = (T) clazz.newInstance();
for (int i = 1; i <= columnCount; i++) {
Object value = resultSet.getObject(i);
String columnName = metaData.getColumnName(i);
String setMethod = "set" + columnName.substring(0, 1).toUpperCase() + columnName.substring(1);
Method method;
if (value instanceof Timestamp) {
method = clazz.getMethod(setMethod, Date.class);
} else {
method = clazz.getMethod(setMethod, value.getClass());
}
method.invoke(obj, value);
}
list.add(obj);
}
} catch (Exception e) {
e.printStackTrace();
}
return list;
}
@Override
public void close() {
if (null == connection) {
return;
}
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
4.SqlSessionFactoryBuilder 用于创建SqlSessionFactory ，解析配置、mapper，创建数据库连接
public class SqlSessionFactoryBuilder {
public DefaultSqlSessionFactory build(Reader reader) {
SAXReader saxReader = new SAXReader();
try {
Document document = saxReader.read(new InputSource(reader));
Configuration configuration = parseConfiguration(document.getRootElement());
return new DefaultSqlSessionFactory(configuration);
} catch (DocumentException e) {
e.printStackTrace();
}
return null;
}
private Configuration parseConfiguration(Element root) {
Configuration configuration = new Configuration();
configuration.setDataSource(dataSource(root.selectNodes("//dataSource")));
configuration.setConnection(connection(configuration.dataSource));
configuration.setMapperElement(mapperElement(root.selectNodes("mappers")));
return configuration;
}
private Map dataSource(List list) {
Map dataSource = new HashMap<>(4);
Element element = list.get(0);
List content = element.content();
for (Object o : content) {
Element e = (Element) o;
String name = e.attributeValue("name");
String value = e.attributeValue("value");
dataSource.put(name, value);
}
return dataSource;
}
private Connection connection(Map dataSource) {
try {
Class.forName(dataSource.get("driver"));
return DriverManager.getConnection(dataSource.get("url"), dataSource.get("username"), dataSource.get("password"));
} catch (ClassNotFoundException | SQLException e) {
e.printStackTrace();
}
return null;
}
private Map mapperElement(List list) {
Map map = new HashMap<>();
Element element = list.get(0);
List content = element.content();
for (Object o : content) {
Element e = (Element) o;
String resource = e.attributeValue("resource");
try {
Reader reader = Resources.getResourceAsReader(resource);
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(new InputSource(reader));
Element root = document.getRootElement();
String namespace = root.attributeValue("namespace");
List selectNodes = root.selectNodes("select");
for (Element node : selectNodes) {
String id = node.attributeValue("id");
String parameterType = node.attributeValue("parameterType");
String resultType = node.attributeValue("resultType");
String sql = node.getText();
Map parameter = new HashMap<>();
Pattern pattern = Pattern.compile("(#\\{(.*?)})");
Matcher matcher = pattern.matcher(sql);
for (int i = 1; matcher.find(); i++) {
String g1 = matcher.group(1);
String g2 = matcher.group(2);
parameter.put(i, g2);
sql = sql.replace(g1, "?");
}
XNode xNode = new XNode();
xNode.setNamespace(namespace);
xNode.setId(id);
xNode.setParameterType(parameterType);
xNode.setResultType(resultType);
xNode.setSql(sql);
xNode.setParameter(parameter);
map.put(namespace + "." + id, xNode);
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
return map;
}
}
5.其他
读取xml文件
public class Resources {
public static Reader getResourceAsReader(String resource) throws IOException {
return new InputStreamReader(getResourceAsStream(resource));
}
private static InputStream getResourceAsStream(String resource) throws IOException {
ClassLoader[] classLoaders = getClassLoaders();
for (ClassLoader classLoader : classLoaders) {
InputStream inputStream = classLoader.getResourceAsStream(resource);
if (null != inputStream) {
return inputStream;
}
}
throw new IOException("Could not find resource " + resource);
}
private static ClassLoader[] getClassLoaders() {
return new ClassLoader[]{
ClassLoader.getSystemClassLoader(),
Thread.currentThread().getContextClassLoader()};
}
}
mapper 结构
public class XNode {
private String namespace;
private String id;
private String parameterType;
private String resultType;
private String sql;
private Map parameter;
}
二.mybatis执行原理
源码解析
@Test
public void test_queryUserInfoById() {
String resource = "mybatis-config-datasource.xml";
Reader reader;
try {
// 1.生成SqlSessionFactory
reader = Resources.getResourceAsReader(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
// 2.获取SqlSession
SqlSession session = sqlSessionFactory.openSession();
try {
// 3.执行查询
UserPo user = session.selectOne("com.example.mybatisstarter.dao.UserDao.queryUserInfoById", 1L);
System.out.println(JSON.toJSONString(user));
} finally {
session.close();
reader.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
1.根据配置文件构建SqlSessionFactory
mybatis-config-datasource.xml 文件
reader = Resources.getResourceAsReader(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
时序图
SqlSessionFactory时序图
2.获取SqlSession
SqlSession session = sqlSessionFactory.openSession();
获取sqlSession时序图
3. 执行查询
UserPo user = session.selectOne("com.example.mybatisstarter.dao.UserDao.queryUserInfoById", 1L);
执行sql时序图
idea时序图生成插件
idea时序图插件