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yang yaru
yang yaru

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Spring Architecture Series-5.Implementing Mybatis Integration

#java #spring

Introduction

MyBatis is a popular persistence framework that provides a flexible way to map SQL statements to Java objects.In this article, I'll explore how to implements MyBatis integration in aSpring-like framework,base on my miniSpring project's implementation.

Core Components

The MyBatis integration consists of several key components:

src/com/yaruyng/batis/ ├── DefaultSqlSessionFactory.java ├── DefaultSqlSession.java ├── SqlSessionFactory.java ├── SqlSession.java └── MapperNode.java
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SqlSessionFactory Implementation

The SqlSessionFactory is the entry point for creating SqlSession instance:

public class DefaultSqlSessionFactory implements SqlSessionFactory { @Autowired JdbcTemplate jdbcTemplate; String mapperLocations; Map<String, MapperNode> mapperNodeMap = new HashMap<>(); public void init() { scanLocation(this.mapperLocations); // Initialize mapper nodes } @Override public SqlSession openSession() { SqlSession newSqlSession = new DefaultSqlSession(); newSqlSession.setJdbcTemplate(jdbcTemplate); newSqlSession.setSqlSessionFactory(this); return newSqlSession; } }
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key features:

  1. Integration with Spring's IoC container
  2. Mapper XML file scanning
  3. Session management

Mapper XML Parsing

The framework parse MyBatis mapper XML files:

private Map<String, MapperNode> buildMapperNodes(String filePath) { SAXReader saxReader = new SAXReader(); URL xmlPath = this.getClass().getClassLoader().getResource(filePath); try { Document document = saxReader.read(xmlPath); Element rootElement = document.getRootElement(); String namespace = rootElement.attributeValue("namespace"); Iterator<Element> nodes = rootElement.elementIterator(); while (nodes.hasNext()) { Element node = nodes.next(); String id = node.attributeValue("id"); String parameterType = node.attributeValue("parameterType"); String resultType = node.attributeValue("resultType"); String sql = node.getText(); MapperNode selectnode = new MapperNode(); selectnode.setNamespace(namespace); selectnode.setId(id); selectnode.setParameterType(parameterType); selectnode.setResultType(resultType); selectnode.setSql(sql); selectnode.setParameter(""); this.mapperNodeMap.put(namespace + "." + id, selectnode); } } catch (Exception ex) { ex.printStackTrace(); } return this.mapperNodeMap; }
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This implementation:

  1. Uses DOM4J for XML parsing
  2. Extracts SQL statements and metadata
  3. Creates MapperNode objects

MapperNode Structure

The MapperNode class represents a single SQL statement:

public class MapperNode { String namespace; String id; String parameterType; String resultType; String sql; String parameter; // Getters and setters }
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Features:

  1. Namespace and ID for unique identification
  2. Parameter and result type information
  3. SQL statement storage
  4. Parameter mapping support

SqlSession Implementation

The DefaultSqlSession handles SQL execution:

public class DefaultSqlSession implements SqlSession { JdbcTemplate jdbcTemplate; SqlSessionFactory sqlSessionFactory; @Override public Object selectOne(String sqlid, Object[] args, PreparedStatementCallBack pstmtcallback) { String sql = this.sqlSessionFactory.getMapperNode(sqlid).getSql(); return jdbcTemplate.query(sql, args, pstmtcallback); } }
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Key aspects:

  1. SQL statement retrieval
  2. Parameter binding
  3. Result mapping
  4. JDBC template integration

Integration with Spring Ioc:

The Mybatis integration leverages Spring's IoC container:

@Autowired JdbcTemplate jdbcTemplate;
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Benefits:

  1. Automatic dependency injection
  2. Transaction management
  3. Connection pooling
  4. Resource management

XML Configuration

Example mapper XML configuration:

<?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.example.UserMapper"> <select id="findById" parameterType="java.lang.Integer" resultType="com.example.User"> SELECT * FROM users WHERE id = ? </select> </mapper>
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Usage Example

Here's how to use the Mybatis integration:

@Repository public class UserDao { @Autowired private SqlSessionFactory sqlSessionFactory; public User findById(Integer id) { SqlSession session = sqlSessionFactory.openSession(); try { return (User) session.selectOne( "com.example.UserMapper.findById", new Object[]{id}, new UserRowMapper() ); } finally { session.close(); } } }
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Key Features

  1. Mapper XML Support
    • XML-Based SQL configuration
    • Dynamic SQL support
    • Parameter mapping
  2. Session Management
    • Connection handing
    • Transaction boundaries
    • Resource cleanup
  3. Result Mapping
    • Object mapping
    • Type conversion
    • Collection handing
  4. Spring Integration
    • IoC container support
    • Transaction management
    • Resource management

Implementation Details

  1. Mapper Scanning 
private void scanLocation(String location) { String sLocation = this.getClass().getClassLoader() .getResource("").getPath() + location; File dir = new File(sLocation); for (File file : dir.listFiles()) { if (file.isDirectory()) { scanLocation(location + "/" + file.getName()); } else { buildMapperNodes(location + "/" + file.getName()); } } }
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  1. SQL Execution 
public Object selectOne(String sqlid, Object[] args, PreparedStatementCallBack pstmtcallback) { String sql = this.sqlSessionFactory.getMapperNode(sqlid).getSql(); return jdbcTemplate.query(sql, args, pstmtcallback); }
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Best Practice

  1. Resource Management
    • Proper session cleanup
    • Connection pooling
    • Transaction boundaries
  2. Error Handling
    • SQL exception handling
    • Resource cleanup in finally blocks
    • Proper error propagation
  3. Performance Optimization
    • Statement caching
    • Connection pooling
    • Batch processing support

Common Challenges and Solutions

  1. Connection Management
    • Use connection pooling
    • Implement proper cleanup
    • Handle transaction boundaries
  2. SQL Mapping
    • Proper parameter binding
    • Result type conversion
    • Collection handling
  3. Transaction Management
    • Spring transaction integration
    • Proper isolation levels
    • Rollback handling

Conclusion

Implementing MyBatis integration in a Spring-like framework provides:

  • Clean separation of concerns
  • Flexible SQL mapping
  • Transaction management
  • Resource optimization Key takeaways:
  • Understanding MyBatis core concepts
  • Spring integration patterns
  • Resource management
  • Performance considerations

This implementation demonstrates how to create a robust ORM framework integration while maintaining simplicity and flexibility.

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