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Eclipse上使用PostgreSQL 9.1和Tomcat 7.连接是通过连接池进行的.当我为PreparedStatement使用setInt()方法时,不返回任何内容.打印PreparedStatement时,’？’被一些奇怪的String取代我想是对象的引用.当我使用方法setObject()和相应的Type.INTEGER时,打印的语句包含正确的值但是作为String,并强制要求Int.

这是代码：

public User_DTO[] select(User_DTO params, int order, int limit, int offset)

{

User_DTO result = null;

ArrayList result_arr = new ArrayList(0);

String query = "SELECT id, name, role FROM Usuario WHERE name LIKE ? AND role LIKE ? AND id != ? ORDER BY ? LIMIT ? OFFSET ?";

String name = params.getName();

String role = params.getRole();

String id = params.getId();

try

{

conn = Pool.getConnection();

stmt = conn.prepareStatement(query);

stmt.setString(1, "%" + name + "%");

stmt.setString(2, "%" + role + "%");

stmt.setString(3, id);

// Using setInt()

// stmt.setInt(4, order);

// Using setObject

stmt.setObject(4, order, Types.INTEGER);

System.out.println(order);

if(limit == -1)

{

stmt.setNull(5, Types.NULL);

}

else

{

stmt.setInt(5, limit);

}

stmt.setInt(6, offset);

//

System.out.println(stmt);

rs = stmt.executeQuery();

while(rs.next())

{

result = new User_DTO();

result.setId(rs.getString("id"));

result.setName(rs.getString("name"));

result.setRole(rs.getString("role"));

result_arr.add(result);

}

}

catch(SQLException sql_e)

{

sql_e.printStackTrace();

}

finally

{

Pool.close(conn, stmt, rs);

}

return (result != null) ? result_arr.toArray(new User_DTO[result_arr.size()]) : null;

}

使用setInt()的打印语句是这样的：

SELECT id, name, role FROM Usuario WHERE name LIKE '%%' AND role LIKE '%%' AND id != '13253cc9' ORDER BY '[B@65adcbab' LIMIT '[B@75167bb3' OFFSET '[B@171360d3'

而使用setObject()打印的那个：

SELECT id, name, role FROM Usuario WHERE name LIKE '%%' AND role LIKE '%%' AND id != '13253cc9' ORDER BY '1' LIMIT '[B@75167bb3' OFFSET '[B@171360d3'

知道为什么会这样吗？

提前致谢！