Beginning Spring学习笔记——第4章（三）将JDBC操作模块化为Java对象

封装SQL查询执行

创建一个扩展自MappingSqlQuery的类来封装用ID查询的SQL操作。

public class AccountByIdQuery extends MappingSqlQuery<Account> {

public AccountByIdQuery(DataSource dataSource) {
super(dataSource,
"select id,owner_name,balance,access_time,locked from account where id = ?");
declareParameter(new SqlParameter(Types.BIGINT));
compile();

}

@Override
protected Account mapRow(ResultSet rs, int rowNum) throws SQLException {
Account account = new Account();
account.setId(rs.getLong("id"));
account.setOwnerName(rs.getString("owner_name"));
account.setBalance(rs.getDouble("balance"));
account.setAccessTime(rs.getTimestamp("access_time"));
account.setLocked(rs.getBoolean("locked"));
return account;
}
}

使用时要先在数据访问实现类中添加MappingSqlQuery类型属性，并传入封装类的值

private MappingSqlQuery<Account> accountByIdQuery;

public void setAccountByIdQuery(MappingSqlQuery<Account> accountByIdQuery) {
this.accountByIdQuery = accountByIdQuery;
}

并在配置文件中注入相关依赖：

@Configuration
public class Ch4Configuration {
@Bean
public DataSource dataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
dataSource.setDriverClassName("org.h2.Driver");
dataSource.setUrl("jdbc:h2:tcp://localhost/~/test");
dataSource.setUsername("sa");
dataSource.setPassword("");
return dataSource;
}

@Bean
public JdbcTemplate jdbcTemplate() {
JdbcTemplate jdbcTemplate = new JdbcTemplate();
jdbc
4000
Template.setDataSource(dataSource());
return jdbcTemplate;
}

@Bean
public AccountDao accountDao() {
AccountDaoJdbcImpl accountDao = new AccountDaoJdbcImpl();
accountDao.setJdbcTemplate(jdbcTemplate());
accountDao.setAccountByIdQuery(accountByIdQuery());
return accountDao;
}

@Bean
public MappingSqlQuery<Account> accountByIdQuery() {
AccountByIdQuery query = new AccountByIdQuery(dataSource());
return query;
}
}

这时实现类中的查找方法就只需要调用封装类实例的方法即可：

public Account find(long accountId) {
return accountByIdQuery.findObject(accountId);
}

封装SQL DML操作

即插入更新和删除操作，三者的封装类都继承自SqlUpdate，如下：

public class AccountInsert extends SqlUpdate {
public AccountInsert(DataSource dataSource) {
super(dataSource,
"insert into account(owner_name,balance,access_time,locked) values(?,?,?,?)");
setParameters(new SqlParameter[] {
new SqlParameter(Types.VARCHAR),
new SqlParameter(Types.DOUBLE),
new SqlParameter(Types.TIMESTAMP),
new SqlParameter(Types.BOOLEAN) });
setReturnGeneratedKeys(true);
setGeneratedKeysColumnNames(new String[]{"id"});
compile();
}
}

public class AccountDelete extends SqlUpdate {
public AccountDelete(DataSource dataSource) {
super(dataSource, "delete account where id = ?");
setParameters(new SqlParameter[]{new SqlParameter(Types.BIGINT)});
compile();
}
}

public class AccountUpdate extends SqlUpdate {
public AccountUpdate(DataSource dataSource) {
super(dataSource,
"update account set (owner_name,balance,access_time,locked) = (?,?,?,?) where id=?");
setParameters(new SqlParameter[] {
new SqlParameter(Types.VARCHAR),
new SqlParameter(Types.DOUBLE),
new SqlParameter(Types.TIMESTAMP),
new SqlParameter(Types.BOOLEAN),
new SqlParameter(Types.BIGINT)});
compile();
}
}

同样需要在配置时注入相应Bean以及实现类中创建相应对象才能使用。

private SqlUpdate accountInsert;
private SqlUpdate accountUpdate;
private SqlUpdate accountDelete;

public void setAccountInsert(SqlUpdate accountInsert) {
this.accountInsert = accountInsert;
}

public void setAccountUpdate(SqlUpdate accountUpdate) {
this.accountUpdate = accountUpdate;
}

public void setAccountDelete(SqlUpdate accountDelete) {
this.accountDelete = accountDelete;
}
//...
public void insert(Account account) {
GeneratedKeyHolder keyHolder = new GeneratedKeyHolder();
int count = accountInsert.update(new Object[]{account.getOwnerName(),account.getBalance(),account.getAccessTime(),account.isLocked()},keyHolder);
if (count != 1)
throw new InsertFailedException("Cannot insert account");
account.setId(keyHolder.getKey().longValue());
}

public void update(Account account) {
int count = accountUpdate.update(account.getOwnerName(),account.getBalance(),account.getAccessTime(),account.isLocked(),account.getId());
if (count != 1)
throw new UpdateFailedException("Cannot update account");
}

public void delete(long accountId) {
int count = accountDelete.update(accountId);
if (count != 1)
throw new DeleteFailedException("Cannot delete account");
}

封装储存过程的执行

这样的封装类扩展自StoredProcedure抽象类

public class ConcatStoredProcedure extends StoredProcedure {
public ConcatStoredProcedure(DataSource dataSource) {
setDataSource(dataSource);
setSql("concat");
declareParameter(new SqlParameter("param1",Types.VARCHAR));
declareParameter(new SqlParameter("param2",Types.VARCHAR));
compile();
}

public String execute(String param1, String param2) {
Map<String,Object> inParams = new HashMap<String,Object>();
inParams.put("param1", param1);
inParams.put("param2", param2);
Map<String, Object> map = execute(inParams);
List<Map> list = (List<Map>) map.get("#result-set-1");
return list.get(0).values().iterator().next().toString();
}
}

在调用compile前使用输入输出参数设置其SQL属性，在公共方法execute中完成操作。

异常处理和错误代码转换

Spring JDBC抛出的所有异常均为DataAccessException的子类，因此只需要一个try-catch代码块就能捕捉任何层的Spring数据访问异常。

可用SQLException Translator将SQL Exception自动转化为DataAccessException。