从SP到复杂对象的java映射结果

1 周，6 日 Questions & Answers 4419

我正在努力在我的工作项目中实施MyBatis。它是一个遗留系统，仅通过存储过程使用普通JDBC访问数据库。我知道要调用存储过程，MyBatis需要一个包含存储过程输入参数的对象和另一个保存结果集的对象。不确定这是否完全正确

为了防止在系统中创建过多的数据实体，我希望重用现有的实体。这就是问题所在。让我解释一下我所面临的典型情况/情景，以及我如何试图解决它

假设系统中有以下数据实体：

class Account { private int accountID; private String accountName; private OrganizationAddress address; // Getters-Setters Go Here } class OrganizationAddress extends Address { // ... some attributes here // Getters-Setters Go Here } class Address { private String address; private String city; private String state; private String country; // Getters-Setters Go Here }

我正在使用注释，所以我的Mapper类有如下内容：

@Select(value = "{call Get_AccountList(#{accountType, mode=IN, jdbcType=String})}") @Options(statementType = StatementType.CALLABLE) @Results(value = { @org.apache.ibatis.annotations.Result (property = "accountID", column = "Account_ID"), @org.apache.ibatis.annotations.Result (property = "accountName", column = "Organization_Name"), @org.apache.ibatis.annotations.Result (property = "state", column = "State", javaType=OrganizationAddress.class) }) List<Account> getAccountList(Param param);

问题：当我调用存储过程时，Account对象的state总是null

此外，我无权访问上述数据实体的来源。所以我也无法尝试在这个链接上提供的解决方案-Mybatis select with nested objects

我的问题是：

我是否可以使用系统中已经存在的数据实体，还是必须创建新的实体，然后将数据映射到现有的实体？

如果是，我该怎么做？任何参考资料，如果有的话
如果没有，有没有办法减少我为调用存储过程而创建的数据实体的数量（对于in和out参数）

# 1 楼答案

我认为最好的解决方案（如果我理解正确的话）是使用MyBatis TypeHandler，它将状态列映射到OrganizationAddress对象

根据你提供的信息，我总结了一个例子，它是有效的。以下是修订后的注释地图：

// Note: you have an error in the @Select line => maps to VARCHAR not "String"
@Select(value = "{call Get_AccountList(#{accountType, mode=IN, jdbcType=VARCHAR})}")
@Options(statementType = StatementType.CALLABLE)
@Results(value = {
  @org.apache.ibatis.annotations.Result
      (property = "accountID", column = "Account_ID"),
  @org.apache.ibatis.annotations.Result
      (property = "accountName", column = "Organization_Name"),
  @org.apache.ibatis.annotations.Result
      (property = "address", column = "State", typeHandler=OrgAddressTypeHandler.class)
  })
List<Account> getAccountList(Param param);

您需要将Account的address字段映射到“state”列，并使用TypeHandler创建一个OrganizationAddress，并填写其“state”属性

我创建的OrgAddressTypeHandler如下所示：

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;

public class OrgAddressTypeHandler extends BaseTypeHandler<OrganizationAddress> {

  @Override
  public OrganizationAddress getNullableResult(ResultSet rs, String colName) throws SQLException {
    OrganizationAddress oa = new OrganizationAddress();
    oa.setState(rs.getString(colName));
    return oa;
  }

  @Override
  public OrganizationAddress getNullableResult(ResultSet rs, int colNum) throws SQLException {
    OrganizationAddress oa = new OrganizationAddress();
    oa.setState(rs.getString(colNum));
    return oa;
  }

  @Override
  public OrganizationAddress getNullableResult(CallableStatement cs, int colNum) throws SQLException {
    OrganizationAddress oa = new OrganizationAddress();
    oa.setState(cs.getString(colNum));
    return oa;
  }

  @Override
  public void setNonNullParameter(PreparedStatement arg0, int arg1, OrganizationAddress arg2, JdbcType arg3) throws SQLException {
    // not needed for this example
  }
}

如果您需要一个比这个更完整的工作示例，我很乐意发送更多。如果我误解了你的例子，请告诉我

有了这个解决方案，你可以不用修改就可以使用你的域对象。只需要TypeHandler来进行映射，而不需要XML映射器文件

我也用MySQL中的MyBatis-3.1.1实现了这一点。下面是我为测试它而创建的简单模式和存储过程：

DROP TABLE IF EXISTS account;
DROP TABLE IF EXISTS organization_address;

CREATE TABLE account (
  account_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
  organization_name VARCHAR(45) NOT NULL,
  account_type VARCHAR(10) NOT NULL,
  organization_address_id SMALLINT UNSIGNED NOT NULL,
  PRIMARY KEY  (account_id)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE organization_address (
  organization_address_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
  address VARCHAR(45) NOT NULL,
  city VARCHAR(45) NOT NULL,
  state VARCHAR(45) NOT NULL,
  country VARCHAR(45) NOT NULL,
  PRIMARY KEY  (organization_address_id)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO organization_address VALUES(1, '123 Foo St.', 'Foo City', 'Texas', 'USA');
INSERT INTO organization_address VALUES(2, '456 Bar St.', 'Bar City', 'Arizona', 'USA');
INSERT INTO organization_address VALUES(3, '789 Quux Ave.', 'Quux City', 'New Mexico', 'USA');

INSERT INTO account VALUES(1, 'Foo',  'Type1', 1);
INSERT INTO account VALUES(2, 'Bar',  'Type1', 2);
INSERT INTO account VALUES(3, 'Quux', 'Type2', 3);

DROP PROCEDURE IF EXISTS Get_AccountList;

DELIMITER $$

CREATE PROCEDURE Get_AccountList(IN p_account_type VARCHAR(10))
READS SQL DATA
BEGIN
     SELECT a.account_id, a.organization_name, o.state
     FROM account a
     JOIN organization_address o ON a.organization_address_id = o.organization_address_id
     WHERE account_type = p_account_type
     ORDER BY a.account_id;
END $$

DELIMITER ;

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从SP到复杂对象的java映射结果

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