MyBatis 四大核心组件之 ParameterHandler 源码解析

@Override
public void setParameters(PreparedStatement ps) throws SQLException {
  // 获取 Java 方法的参数对象
  Object parameterObject = getParameterObject();
  // 获取当前正在执行的 SQL 语句的映射语句
  MappedStatement mappedStatement = getMappedStatement();
  // 获取 SQL 语句中的参数映射
  List<ParameterMapping> parameterMappings = mappedStatement.getParameterMappings();
  // 遍历参数映射
  for (int i = 0; i < parameterMappings.size(); i++) {
    // 获取参数映射
    ParameterMapping parameterMapping = parameterMappings.get(i);
    // 获取参数值
    Object value = getParameterValue(parameterMapping, parameterObject);
    // 设置参数值
    ps.setObject(i + 1, value);
  }
}

private Object getParameterValue(ParameterMapping parameterMapping, Object parameterObject) {
  // 获取参数类型
  Class<?> parameterType = parameterMapping.getJavaType();
  // 获取参数名称
  String parameterName = parameterMapping.getProperty();
  // 获取参数值
  Object value = null;
  if (parameterType == String.class) {
    value = (String) parameterObject;
  } else if (parameterType == Integer.class) {
    value = (Integer) parameterObject;
  } else if (parameterType == Long.class) {
    value = (Long) parameterObject;
  } else if (parameterType == Float.class) {
    value = (Float) parameterObject;
  } else if (parameterType == Double.class) {
    value = (Double) parameterObject;
  } else if (parameterType == Date.class) {
    value = (Date) parameterObject;
  } else if (parameterType == byte[].class) {
    value = (byte[]) parameterObject;
  } else {
    // 如果参数类型是复杂类型，则需要使用反射获取参数值
    try {
      Field field = parameterObject.getClass().getDeclaredField(parameterName);
      field.setAccessible(true);
      value = field.get(parameterObject);
    } catch (NoSuchFieldException e) {
      throw new RuntimeException("Error getting parameter value: " + e.getMessage());
    } catch (IllegalAccessException e) {
      throw new RuntimeException("Error getting parameter value: " + e.getMessage());
    }
  }
  // 返回参数值
  return value;
}