编码问题我仍旧没搞懂，最根本的从哪里来就没搞懂。当页面发送请求，编码到后台是什么编码呢？好吧，我默认的都是utf-8.后台接收参数后，可以在控制台打印出来，我也不清楚是什么编码。然后，就是数据库问题。
在mysql数据库，首先会设置mysql安装的字符集为utf-8,然后在连接的jdbc上注明characterEncoding是utf-8.一直这样统一下去，没有出现乱码。
连接oracle就出现问题了，我使用的一个已经安装好的oracle数据库。字符集是American，us7ascii.我插入和查询的中文都是乱码。百度了很久之后，还是进行转码工作。
关于java编码，先看String中的几个方法：
getBytes()
1 byte[] java.lang.String.getBytes(String charsetName) throws UnsupportedEncodingException 2 3 4 Encodes this String into a sequence of bytes using the named charset, storing the result into a new byte array. 5 6 The behavior of this method when this string cannot be encoded in the given charset is unspecified. The java.nio.charset.CharsetEncoder class should be used when more control over the encoding process is required.
这里先要搞清楚编码(encode)和解码(decode).下面是个人推测，没有考证的解释：
encode:编码，将字符依据某种规则(字符集)解释为一串数字
decode:解码，将一串数字依据某种规则翻译为字符
理解了编码和解码后，从一个字符串开始解析。
字符串str="中文"，str是一串字符，通过str.getBytes()可以编码成byte数组。通过new String(bytes)来解码为字符串。下面是测试：
1 @Test 2 public void getEncod() throws UnsupportedEncodingException { 3 String sysencod = System.getProperty("file.encoding"); 4 System.out.println("系统默认编码："+sysencod); 5 String str = "中文"; 6 System.out.println("字符实例："+str); 7 System.out.println("===============getbytes无参:==============="); 8 byte[] bytes = str.getBytes(); 9 for (int i = 0; i < bytes.length; i++) { 10 System.out.print(bytes[i]); 11 } 12 System.out.println(); 13 System.out.println("通过默认字符集，将字符数组解码为字符："+new String(bytes)); 14 System.out.println("通过utf-8字符集，将字符数组解码为字符："+new String(bytes,"utf-8")); 15 System.out.println("通过gbk字符集，将字符数组解码为字符："+new String(bytes,"gbk")); 16 System.out.println("通过iso-8859-1字符集，将字符数组解码为字符："+new String(bytes,"iso-8859-1")); 17 18 19 System.out.println("===============getbytes(utf-8):==============="); 20 byte[] bytes2 = str.getBytes("utf-8"); 21 for (int i = 0; i < bytes.length; i++) { 22 System.out.print(bytes[i]); 23 } 24 System.out.println(); 25 System.out.println("通过默认字符集，将字符数组解码为字符："+new String(bytes2)); 26 System.out.println("通过utf-8字符集，将字符数组解码为字符："+new String(bytes2,"utf-8")); 27 System.out.println("通过gbk字符集，将字符数组解码为字符："+new String(bytes2,"gbk")); 28 System.out.println("通过iso-8859-1字符集，将字符数组解码为字符："+new String(bytes2,"iso-8859-1")); 29 System.out.println("===============getbytes(gbk):==============="); 30 byte[] bytes3 = str.getBytes("gbk"); 31 for (int i = 0; i < bytes.length; i++) { 32 System.out.print(bytes[i]); 33 } 34 System.out.println(); 35 System.out.println("通过默认字符集，将字符数组解码为字符："+new String(bytes3)); 36 System.out.println("通过utf-8字符集，将字符数组解码为字符："+new String(bytes3,"utf-8")); 37 System.out.println("通过gbk字符集，将字符数组解码为字符："+new String(bytes3,"gbk")); 38 System.out.println("通过iso-8859-1字符集，将字符数组解码为字符："+new String(bytes3,"iso-8859-1")); 39 System.out.println("===============getbytes(iso-8859-1):==============="); 40 byte[] bytes4 = str.getBytes("iso-8859-1"); 41 for (int i = 0; i < bytes.length; i++) { 42 System.out.print(bytes[i]); 43 } 44 System.out.println(); 45 System.out.println("通过默认字符集，将字符数组解码为字符："+new String(bytes4)); 46 System.out.println("通过utf-8字符集，将字符数组解码为字符："+new String(bytes4,"utf-8")); 47 System.out.println("通过gbk字符集，将字符数组解码为字符："+new String(bytes4,"gbk")); 48 System.out.println("通过iso-8859-1字符集，将字符数组解码为字符："+new String(bytes4,"iso-8859-1")); 49 }