自定义持久层框架设计思路：
使用端：（项目） 引入持久层框架（jar包）
提供两部分配置信息：数据库配置信息，sql配置信息：SQL语句、参数类型、返回值类型 使用配置文件来提供：
1、 SqlMapConfig.xml：存放数据库配置，存放mapper.xml全路径 (存放mapper.xml全路径只要是为了值传递一个path)
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<dataSource>
<property name="driverClass" value="com.mysql.cj.jdbc.Driver"></property>
<property name="jdbcUrl" value="jdbc:mysql://localhost:3306/zdy_mybatis?characterEncoding=utf8&useSSL=false&serverTimezone=Asia/Shanghai"></property>
<property name="username" value="root"></property>
<property name="password" value="root"></property>
</dataSource>
<mapper resource="UserMapper.xml"></mapper>
</configuration>
2、 mapper.xml：存放sql配置信息
<?xml version="1.0" encoding="utf-8"?>
<mapper namespace="com.jdbc_test.dao.IUserDao">
<select id="findAll" resultType="com.jdbc_test.pojo.User">
select * from user
</select>
<select id="findByConditions" resultType="com.jdbc_test.pojo.User" paramType="com.jdbc_test.pojo.User">
select * from user where id = #{id} and username = #{username}
</select>
</mapper>
自定义持久层框架：本质就是对jdbc进行封装
1、 加载配置文件：根据路径，加载为字节输入流，存在内存中
创建Resource类 方法：InputStream getResourceAsStream（String path）
public class Resource {
public static InputStream getResourceAsStream(String path) {
return Resource.class.getClassLoader().getResourceAsStream(path);
}
}
2、 创建两个JavaBean （容器对象） 用来存储对配置文件解析出来的内容
（1）Configuration：核心配置类，存放sqlMapConfig.xml中的数据库基本信息，Map<唯一标识, Mapper> 唯一标识： namespace.id
public class Configuration {
private DataSource dataSource;
Map<String, MappedStatement> map = new HashMap<String, MappedStatement>();
public DataSource getDataSource() {
return dataSource;
}
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
public Map<String, MappedStatement> getMap() {
return map;
}
public void setMap(Map<String, MappedStatement> map) {
this.map = map;
}
}
（2）MappedStatement：映射配置类，存放mapper.xml中解析出来的SQL语句、id、参数类型、返回值类型、statement类型
public class MappedStatement {
private String id;
private String paramterType;
private String resultType;
private String sql;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getParamterType() {
return paramterType;
}
public void setParamterType(String paramterType) {
this.paramterType = paramterType;
}
public String getResultType() {
return resultType;
}
public void setResultType(String resultType) {
this.resultType = resultType;
}
public String getSql() {
return sql;
}
public void setSql(String sql) {
this.sql = sql;
}
}
3、 解析配置文件： dom4j
创建类：SQLSessionFactoryBuilder: build(InputStream in);
(1) 使用dom4j解析配置文件，将解析出来的内容封装到容器对象
public class XMLConfigBuilder {
private Configuration configuration;
public XMLConfigBuilder() {
this.configuration = new Configuration();
}
public Configuration parse(InputStream in) throws DocumentException, PropertyVetoException, NamingException {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(in);
//解析configuration
Element configurationElement = document.getRootElement();
List<Element> propertyList = configurationElement.selectNodes("//property");
Properties properties = new Properties();
for (Element element : propertyList) {
String name = element.attributeValue("name");
String value = element.attributeValue("value");
properties.setProperty(name, value);
}
ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();
comboPooledDataSource.setDriverClass(properties.getProperty("driverClass"));
comboPooledDataSource.setJdbcUrl(properties.getProperty("jdbcUrl"));
comboPooledDataSource.setUser(properties.getProperty("username"));
comboPooledDataSource.setPassword(properties.getProperty("password"));
this.configuration.setDataSource(comboPooledDataSource);
//解析mapper
List<Element> mapperList = configurationElement.selectNodes("//mapper");
for (Element element : mapperList) {
String mapperFilePath = element.attributeValue("resource");
InputStream resourceAsStream = Resource.getResourceAsStream(mapperFilePath);
XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(this.configuration);
xmlMapperBuilder.parse(resourceAsStream);
}
return this.configuration;
}
}
public class XMLMapperBuilder {
private Configuration configuration;
public XMLMapperBuilder(Configuration configuration) {
this.configuration = configuration;
}
public void parse(InputStream inputStream) throws DocumentException {
Document document = new SAXReader().read(inputStream);
//解析mappedStatement <mapper namespace="user">
Element mappedStatementElement = document.getRootElement();
String namespace = mappedStatementElement.attributeValue("namespace");
List<Element> selectList = mappedStatementElement.selectNodes("//select");
for (Element element : selectList) {
MappedStatement mappedStatement = new MappedStatement();
String id = element.attributeValue("id");
String resultType = element.attributeValue("resultType");
String paramType = element.attributeValue("paramType");
String sql = element.getTextTrim();
mappedStatement.setId(id);
mappedStatement.setParamterType(paramType);
mappedStatement.setResultType(resultType);
mappedStatement.setSql(sql);
this.configuration.getMappedStatementMap().put(namespace + "." + id, mappedStatement);
}
}
}
(2) 创建SQLSessionFactory对象，生产SQLSession： 会话对象（工厂模式）
public class SqlSessionFactoryBuilder {
public SqlSessionFactory build(InputStream in) throws Exception {
XMLConfigBuilder xmlConfigBuilder = new XMLConfigBuilder();
Configuration configuration = xmlConfigBuilder.parse(in);
SqlSessionFactory sqlSessionFactory = new DefaultSqlSessionFactory(configuration);
return sqlSessionFactory;
}
}
4、 创建SQLSessionFactory接口及实现类DefaultSQLSessionFactory
openSession(): 生产SqlSession
public interface SqlSessionFactory {
SqlSession openSession();
}
public class DefaultSqlSessionFactory implements SqlSessionFactory {
private Configuration configuration;
public DefaultSqlSessionFactory(Configuration configuration) {
this.configuration = configuration;
}
public SqlSession openSession() {
return new DefaultSqlSession(this.configuration);
}
}
5、 创建SqlSession接口及实现类DefaultSqlSession
定义对数据库的crud操作：
insert()
selectList()
selectOne()
update()
delete()
public interface SqlSession {
<E> List<E> selectList(String statementId, Object...param) throws Exception;
<T> T selectOne(String statementId, Object...param) throws Exception;
//为Dao接口生成代理实现类
public <T> T getMapper(Class<?> mapperClass);
}
public class DefaultSqlSession implements SqlSession {
private Configuration configuration;
public DefaultSqlSession(Configuration configuration) {
this.configuration = configuration;
}
@Override
public <E> List<E> selectList(String statementId, Object...params) throws Exception {
SampleExecutor sampleExecutor = new SampleExecutor();
List<E> result = sampleExecutor.query(this.configuration, this.configuration.getMappedStatementMap().get(statementId), params);
return result;
}
@Override
public <T> T selectOne(String statementId, Object...params) throws Exception {
List<Object> objects = this.selectList(statementId, params);
if (objects.size() == 1) {
return (T) objects.get(0);
} else {
throw new RuntimeException("查询结果为空或者多个");
}
}
@Override
public <T> T getMapper(Class<?> mapperClass) {
Object instance = Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
String methodName = method.getName();
String name = method.getDeclaringClass().getName();
Type genericReturnType = method.getGenericReturnType();
//genericReturnType instanceof ParameterizedType 返回值类型是个列表
if (genericReturnType instanceof ParameterizedType) {
return selectList(name+"."+methodName, args);
}
return selectOne(name+"."+methodName, args);
}
});
return (T) instance;
}
}
6、 创建Executor接口及实现类SimpleExecutor
query(Configuration, MappedStatement, Object...params) 执行的就是jdbc代码
public interface Executor {
<E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object...params) throws Exception;
}
public class SampleExecutor implements Executor {
public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object[] params) throws Exception {
// 1. 获取连接
Connection connection = configuration.getDataSource().getConnection();
// 2. 获取boundSql
BoundSql boundSql = this.getBoundSql(mappedStatement);
// 3. 预处理对象
PreparedStatement ps = connection.prepareStatement(boundSql.getSql());
// 4. 设置参数
String paramterType = mappedStatement.getParamterType();
Class paramterClazz = getClassType(paramterType);
List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
for (int i = 0; i < parameterMappingList.size(); i++) {
ParameterMapping parameterMapping = parameterMappingList.get(i);
//字段名称
String content = parameterMapping.getContent();
//通过字段名称 在param中获取字段的值
Field declaredField = paramterClazz.getDeclaredField(content);
//设置暴力访问
declaredField.setAccessible(true);
//字段对应的值
Object o = declaredField.get(params[0]);
//设置对应位置‘?’占位符的参数
ps.setObject(i + 1, o);
}
// 5. 执行sql
ResultSet resultSet = ps.executeQuery();
// 6. 封装返回结果
String resultType = mappedStatement.getResultType();
Class resultClazz = this.getClassType(resultType);
//用来保存结果集
List<Object> list = new ArrayList<Object>();
while (resultSet.next()) {
Object instance = resultClazz.newInstance();
ResultSetMetaData metaData = resultSet.getMetaData();
for (int i = 1; i <= metaData.getColumnCount(); i++) {
//字段名
String columnName = metaData.getColumnName(i);
//字段值
Object result = resultSet.getObject(columnName);
//使用反射或者内省，根据数据库表和实体的对应关系，完成封装
PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultClazz);
propertyDescriptor.getWriteMethod().invoke(instance, result);
}
list.add(instance);
}
return (List<E>) list;
}
private Class getClassType(String paramterType) throws ClassNotFoundException {
if (null != paramterType) {
Class<?> clazz = Class.forName(paramterType);
return clazz;
}
return null;
}
private BoundSql getBoundSql(MappedStatement mappedStatement) {
// 1. 获取sql 带占位符的
String sql = mappedStatement.getSql();
// 2. 解析sql
ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
String parseSql = genericTokenParser.parse(sql);
return new BoundSql(parseSql, parameterMappingTokenHandler.getParameterMappings());
}
}
7、 编写测试类，测试代码
public class IPersistenceTest {
@Test
public void test1() throws Exception {
InputStream resourceAsStream = Resource.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
// List<User> userList = sqlSession.selectList("user.selectList");
// userList.forEach(user -> {
// System.out.println(user);
// });
User user = new User();
user.setId(1);
user.setUsername("lucy");
User o = sqlSession.selectOne("user.selectOne", user);
System.out.println(o);
}
@Test
public void test2() throws Exception {
IUserDaoImpl iUserDao = new IUserDaoImpl();
List<User> all = iUserDao.findAll();
all.forEach(user -> {
System.out.println(user);
});
}
@Test
public void test3() throws Exception {
InputStream resourceAsStream = Resource.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
IUserDao mapper = sqlSession.getMapper(IUserDao.class);
List<User> all = mapper.findAll();
all.forEach(user -> {
System.out.println(user);
});
}
}
8、 过程中文件
BoundSql
public class BoundSql {
private String sql;
private List<ParameterMapping> parameterMappingList;
public BoundSql(String sql, List<ParameterMapping> parameterMappingList) {
this.sql = sql;
this.parameterMappingList = parameterMappingList;
}
public String getSql() {
return sql;
}
public void setSql(String sql) {
this.sql = sql;
}
public List<ParameterMapping> getParameterMappingList() {
return parameterMappingList;
}
public void setParameterMappingList(List<ParameterMapping> parameterMappingList) {
this.parameterMappingList = parameterMappingList;
}
}
User
public class User {
private int id;
private String username;
public int getId() {
return id;
}
public void setId(int 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 + '\'' +
'}';
}
}
IUserDaoImpl
public class IUserDaoImpl implements IUserDao {
@Override
public List<User> findAll() throws Exception {
InputStream resourceAsStream = Resource.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
List<User> userList = sqlSession.selectList("user.selectList");
return userList;
}
@Override
public User findByConditions(User user) throws Exception {
InputStream resourceAsStream = Resource.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
user.setId(1);
user.setUsername("lucy");
User o = sqlSession.selectOne("user.selectOne", user);
System.out.println(o);
return o;
}
}
user.sql
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(50) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8