Java-22 深入浅出 MyBatis - 手写ORM框架3 手写SqlSession、Executor 工作 - ToB企服应用市场:ToB评测及商务社交产业平台

public class SqlSessionFactoryBuilder {
private Configuration configuration;
public SqlSessionFactoryBuilder() {
configuration = new Configuration();
}
public SqlSessionFactory build(InputStream inputStream) throws DocumentException, PropertyVetoException, ClassNotFoundException {
XMLConfigerBuilder xmlConfigerBuilder = new XMLConfigerBuilder(configuration);
Configuration conf = xmlConfigerBuilder.parseConfiguration(inputStream);
return new DefaultSqlSessionFactory(conf);
}
}

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public interface SqlSessionFactory {
SqlSession openSession();
}

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public interface SqlSession {
<E> List<E> selectList(String statementId, Object ...params) throws Exception;
<T> T selectOne(String statementId, Object ...params) throws Exception;
void close() throws Exception;
}

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@AllArgsConstructor
public class DefaultSqlSession implements SqlSession {
private Configuration configuration;
private Executor simpleExecutor = new SimpleExecutor();
public DefaultSqlSession(Configuration configuration) {
this.configuration = configuration;
}
@Override
public <E> List<E> selectList(String statementId, Object... params) throws Exception {
MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
// System.out.println("DefaultSqlSession => selectList => + " + "statementId: " + statementId + ", mappedStatement: " + mappedStatement);
return simpleExecutor.query(configuration, mappedStatement, params);
}
@Override
public <T> T selectOne(String statementId, Object... params) throws Exception {
List<Object> objects = selectList(statementId, params);
if (objects.size() == 1) {
return (T) objects.get(0);
}
throw new RuntimeException("DefaultSqlSession selectOne 返回结果不唯一: " + statementId);
}
@Override
public void close() throws Exception {
simpleExecutor.close();
}
@Override
public <T> T getMapper(Class<?> mapperClass) {
Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
String methodName = method.getName();
if (method.getDeclaringClass() == Object.class) {
return method.invoke(this, args);
}
String className = method.getDeclaringClass().getName();
String statementId = className + "." + methodName;
Type genericReturnType = method.getGenericReturnType();
if(genericReturnType instanceof ParameterizedType){
List<Object> objects = selectList(statementId, args);
return objects;
}
return selectOne(statementId,args);
}
});
return (T) proxyInstance;
}
}

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public interface Executor {
<E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object[] params) throws Exception;
void close() throws Exception;
}

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public class SimpleExecutor implements Executor {
private Connection connection;
@Override
public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object[] params) throws Exception {
connection = configuration.getDataSource().getConnection();
String sql = mappedStatement.getSql();
BoundSql boundSql = getBoundSql(sql);
PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
String parameterType = mappedStatement.getParameterType();
Class<?> parameterTypeClass = getClassType(parameterType);
List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
int n = 0;
for (ParameterMapping pm : parameterMappingList) {
String content = pm.getName();
Field declaredField = parameterTypeClass.getDeclaredField(content);
declaredField.setAccessible(true);
Object object = declaredField.get(params[0]);
preparedStatement.setObject(n + 1, object);
}
// 执行sql
ResultSet resultSet = preparedStatement.executeQuery();
String resultType = mappedStatement.getResultType();
Class<?> resultTypeClass = getClassType(resultType);
List<Object> objects = new ArrayList<>();
// 封装返回结果集
while (resultSet.next()) {
Object o = resultTypeClass.newInstance();
// 元数据
ResultSetMetaData metaData = resultSet.getMetaData();
for (int i = 1; i <= metaData.getColumnCount(); i ++) {
// 字段名
String columnName = metaData.getColumnName(i);
// 字段的值
Object value = resultSet.getObject(columnName);
// 反射根据数据库和实体完成
PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
Method writeMethod = propertyDescriptor.getWriteMethod();
writeMethod.invoke(o, resultTypeClass.getDeclaredField(columnName).getType().cast(value));
}
objects.add(o);
}
return (List<E>) objects;
}
private BoundSql getBoundSql(String sql) {
// 标记处理类配置标记解析器来完成对占位符的解析处理工作
ParameterMappingTokenHandler parameterMappingHandler = new ParameterMappingTokenHandler();
GenericTokenParser genericTokenParser = new GenericTokenParser(
"#{", "}",
parameterMappingHandler
);
// 解析出来的sql
String parseSql = genericTokenParser.parse(sql);
// #{} 里边的参数
List<ParameterMapping> parameterMapping = parameterMappingHandler.getParameterMappings();
BoundSql boundSql = new BoundSql(parseSql, parameterMapping);
System.out.println("SimpleExecutor getBoundSql: " + boundSql.getSqlText());
return boundSql;
}
private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
if(parameterType != null){
return Class.forName(parameterType);
}
return null;
}
@Override
public void close() throws Exception {
connection.close();
}
}

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connection = configuration.getDataSource().getConnection();

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