以下是程序中用到的方法
// 写入数据
public static StringBuffer writeCsv(
List<LinkedHashMap<String, Object>> mapList, String csvstr)
throws Exception {
StringBuffer logsb = new StringBuffer();
FileOutputStream out = null;
OutputStreamWriter osw = null;
BufferedWriter bw = null;
try {
File csvfile = new File(csvstr); // logFile 是路径，就叫做String logFile
// 生成路径+想要的文件名+".csv";
//System.out.println(csvstr);
out = new FileOutputStream(csvfile);
osw = new OutputStreamWriter(out, "GB2312");
bw = new BufferedWriter(osw);
// CSV默认是已逗号","分隔单元格的。这里是表头
if (mapList.size() > 0) {
// 表头
// System.out.println("开始写表头");
String content = "";
for (Entry<String, Object> entry : mapList.get(0).entrySet()) {
content += entry.getKey() + ",";
}
bw.write(content + "\r\n");
// System.out.println("表头写入完成");
// System.out.println("开始写入内容");
// 数据
for (int i = 0; i < mapList.size(); i++) {
String datastr = "";
HashMap<String, Object> propertymap = mapList.get(i);
for (Entry<String, Object> entry : propertymap.entrySet()) {
String obj = entry.getValue() + "";
if (obj.contains("oracle.sql.CLOB")) {
obj = oracleclobToString(entry.getValue());
}
if (obj.contains("\"")) {
obj = obj.replace("\"", "\"\"");
}
if (obj.contains(",")) {
obj = "\"" + obj + "\"";
}
datastr += obj + ",";
}
bw.write(datastr + "\r\n");
bw.flush();
}
// System.out.println("内容写入完成");
}
logsb.append("INFO 导入CSV共" + mapList.size() + "行\r\n");
} catch (Exception e) {
throw e;
} finally {
bw.close();
osw.close();
out.close();
}
return logsb;
}
// CLOB数据转换成String
// oracle.sql.Clob类型转换成String类型
public static String oracleclobToString(Object objclob) throws Exception {
String reString = "";
Clob clob = (Clob) objclob;
Reader is = clob.getCharacterStream();// 得到流
BufferedReader br = new BufferedReader(is);
String s = br.readLine();
StringBuffer sb = new StringBuffer();
while (s != null) {// 执行循环将字符串全部取出付值给StringBuffer由StringBuffer转成STRING
sb.append(s);
s = br.readLine();
}
reString = sb.toString();
return reString;
}
此处注意的是
1、数据库中字段的类型如果是Clob类型的话，则需要转换成String类型，否则写入到csv中是无法看到数据
2、写入CSV文件中的字段值里面的有双引号的则需要转换，否则写入数据格式就错开，转换方式则是用两个双引号替换，替换后则写出后还是一个双引号
3、写入的时候，最好一行一行写入，否则数据多的时候会包溢出
// CLOB数据转换成String // oracle.sql.Clob类型转换成String类型
此方法可以用到备份数据，导出csv文件用到，