Yyds dry inventory executor package (parameter processing function)

executor package （ Parameter processing function ）

sql The parameter assignment in the statement is made by executor In bag parameter Sub package completed .

parameter There is only one sub bag parameterHandler Interface , It defines the 2 A way ：

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       public interface ParameterHandler {
       
       

       
       
  Object getParameterObject();
       
       

       
       
  void setParameters(PreparedStatement ps)
       
       
      throws SQLException;
       
       

       
       
}
      
      
      
      

       
       
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ParameterHandler Interface has a default implementation class DefaultParameterHandler, It's in scripting In the sub package of the package .

mybatis The statement type that supports parameter setting in is PreparedStatement Interfaces and their sub interfaces CallableStatement, therefore setParameters The input parameter for is PreparedStatement type .

setParameters The implementation logic of the method is to take out the value of each parameter in turn , Then call according to the parameter type PreparedStatement The assignment method in .

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       public class DefaultParameterHandler implements ParameterHandler {
       
       
  //  Type processor registry 
       
       
  private final TypeHandlerRegistry typeHandlerRegistry;
       
       
  // MappedStatement object （ It contains complete node information of addition, deletion, modification and query ）
       
       
  private final MappedStatement mappedStatement;
       
       
  //  Parameter object 
       
       
  private final Object parameterObject;
       
       
  // BoundSql object （ contain SQL sentence 、 Parameters 、 Argument information ）
       
       
  private final BoundSql boundSql;
       
       
  //  Configuration information 
       
       
  private final Configuration configuration;
       
       

       
       
  public DefaultParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
       
       
    this.mappedStatement = mappedStatement;
       
       
    this.configuration = mappedStatement.getConfiguration();
       
       
    this.typeHandlerRegistry = mappedStatement.getConfiguration().getTypeHandlerRegistry();
       
       
    this.parameterObject = parameterObject;
       
       
    this.boundSql = boundSql;
       
       
  }
       
       

       
       
  @Override
       
       
  public Object getParameterObject() {
       
       
    return parameterObject;
       
       
  }
       
       

       
       
  /**
       
       
   *  Set parameters for the statement 
       
       
   * @param ps  sentence 
       
       
   */
       
       
  @Override
       
       
  public void setParameters(PreparedStatement ps) {
       
       
    ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
       
       
    //  Take out the parameter list 
       
       
    List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
       
       
    if (parameterMappings != null) {
       
       
      for (int i = 0; i < parameterMappings.size(); i++) {
       
       
        ParameterMapping parameterMapping = parameterMappings.get(i);
       
       
        // ParameterMode.OUT yes CallableStatement The output parameters of , Already registered separately . So ignore 
       
       
        if (parameterMapping.getMode() != ParameterMode.OUT) {
       
       
          Object value;
       
       
          //  Take out the attribute name 
       
       
          String propertyName = parameterMapping.getProperty();
       
       
          if (boundSql.hasAdditionalParameter(propertyName)) {
       
       
            //  Read attribute values from additional parameters 
       
       
            value = boundSql.getAdditionalParameter(propertyName);
       
       
          } else if (parameterObject == null) {
       
       
            value = null;
       
       
          } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
       
       
            //  Parameter objects are basic types , Then the parameter object is the parameter value 
       
       
            value = parameterObject;
       
       
          } else {
       
       
            //  Parameter objects are complex types , Get the attribute value of the parameter object 
       
       
            MetaObject metaObject = configuration.newMetaObject(parameterObject);
       
       
            value = metaObject.getValue(propertyName);
       
       
          }
       
       
          //  The processor that determines this parameter 
       
       
          TypeHandler typeHandler = parameterMapping.getTypeHandler();
       
       
          JdbcType jdbcType = parameterMapping.getJdbcType();
       
       
          if (value == null && jdbcType == null) {
       
       
            jdbcType = configuration.getJdbcTypeForNull();
       
       
          }
       
       
          try {
       
       
            //  This method finally depends on the parameter type , call java.sql.PreparedStatement Parameter assignment method in class , Yes SQL Parameter assignment in a statement 
       
       
            typeHandler.setParameter(ps, i + 1, value, jdbcType);
       
       
          } catch (TypeException | SQLException e) {
       
       
            throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);
       
       
          }
       
       
        }
       
       
      }
       
       
    }
       
       
  }
       
       

       
       
}
      
      
      
      

       
       
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