【IT168技术文档】在J2ME中，RMS作为唯一的永久性存储工具，其重要性是不言而喻的。但是很多刚刚开始学习J2ME的新人总是抱怨在这方面的资料很少，或者是针对性不强。因此，我想把自己在这方面的一些学习心得和大家交流一下。
RMS即Record Manager System，在手机应用中常常作为得分记录、游戏信息存储等的工具使用。
RMS的使用可以分为两个部分：一、单一记录的构造;二、RecordStore的使用和操作。下面就这两方面进行详细说明。
一、单一记录的构造。我们在存储记录时可能需要记录很多相似的条目，在这里我们可以把这种结构看成数据库，我们在这一步就是要构造数据库中的一行，即单一记录的构造。程序的源码如下：
package com.cuilichen.usual;
import java.io.ByteArrayInputStream;//要使用到的各种输入输出流
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
public class Appointment {//单一记录的类名
private int int1; //
private int int2; //
private long long1;
private String str1; //str1作为保留字段，记录检索的关键字
private String str2; //
private String str3; //
private boolean WroteFlag; //
public Appointment() {
}
public Appointment(int _int1, int _int2, long _long1, String _str1,
String _str2, String _str3, boolean _WroteFlag) {
this.int1 = _int1; //写入RMS的构造函数
this.int2 = _int2;
this.long1 = _long1;
this.str1 = _str1;
this.str2 = _str2;
this.str3 = _str3;
this.WroteFlag = _WroteFlag;
}
public Appointment(byte[] rec) {
initAppointmnet(rec); //读取RMS内容的构造函数
}
public byte[] toBytes() { //写成字节
byte[] data = null;
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
dos.writeInt(int1);
dos.writeInt(int2);
dos.writeLong(long1);
dos.writeUTF(str1);
dos.writeUTF(str2);
dos.writeUTF(str3);
dos.writeBoolean(WroteFlag);
data = baos.toByteArray();
baos.close();
dos.close();
} catch (Exception e) {
e.printStackTrace();
}
return data;
}
public void initAppointmnet(byte[] rec) { //从字节读取内容
ByteArrayInputStream bais = new ByteArrayInputStream(rec);
DataInputStream dis = new DataInputStream(bais);
try {
int1 = dis.readInt();
int2 = dis.readInt();
long1 = dis.readLong();
str1 = dis.readUTF();
str2 = dis.readUTF();
str3 = dis.readUTF();
WroteFlag = dis.readBoolean();
} catch (Exception e) {
e.printStackTrace();
}
}
public int getInt1() { //int
return int1;
}
public int getInt2() {
return int2;
}
public long getLong1() {
return long1;
}
public String getStr1() { //String
return str1;
}
public String getStr2() { //String
return str2;
}
public String getStr3() {
return str3;
}
public boolean getWroteFlag() { //返回写入标志
return WroteFlag;
}
}
import java.io.ByteArrayInputStream;//要使用到的各种输入输出流
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
public class Appointment {//单一记录的类名
private int int1; //
private int int2; //
private long long1;
private String str1; //str1作为保留字段，记录检索的关键字
private String str2; //
private String str3; //
private boolean WroteFlag; //
public Appointment() {
}
public Appointment(int _int1, int _int2, long _long1, String _str1,
String _str2, String _str3, boolean _WroteFlag) {
this.int1 = _int1; //写入RMS的构造函数
this.int2 = _int2;
this.long1 = _long1;
this.str1 = _str1;
this.str2 = _str2;
this.str3 = _str3;
this.WroteFlag = _WroteFlag;
}
public Appointment(byte[] rec) {
initAppointmnet(rec); //读取RMS内容的构造函数
}
public byte[] toBytes() { //写成字节
byte[] data = null;
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
dos.writeInt(int1);
dos.writeInt(int2);
dos.writeLong(long1);
dos.writeUTF(str1);
dos.writeUTF(str2);
dos.writeUTF(str3);
dos.writeBoolean(WroteFlag);
data = baos.toByteArray();
baos.close();
dos.close();
} catch (Exception e) {
e.printStackTrace();
}
return data;
}
public void initAppointmnet(byte[] rec) { //从字节读取内容
ByteArrayInputStream bais = new ByteArrayInputStream(rec);
DataInputStream dis = new DataInputStream(bais);
try {
int1 = dis.readInt();
int2 = dis.readInt();
long1 = dis.readLong();
str1 = dis.readUTF();
str2 = dis.readUTF();
str3 = dis.readUTF();
WroteFlag = dis.readBoolean();
} catch (Exception e) {
e.printStackTrace();
}
}
public int getInt1() { //int
return int1;
}
public int getInt2() {
return int2;
}
public long getLong1() {
return long1;
}
public String getStr1() { //String
return str1;
}
public String getStr2() { //String
return str2;
}
public String getStr3() {
return str3;
}
public boolean getWroteFlag() { //返回写入标志
return WroteFlag;
}
}
这个类的使用保证了我们在使用流时，内容的写入和输出。当然，就如同数据库表的设计一样，我们可以任意对每一条记录增加或减少字段，在上面的类中我只使用了int1，int2，long1，str1，str2，str3和WroteFlag一共7个字段。
二、RecordStore的操作。类RMS如下：
package com.cuilichen.usual;
import javax.microedition.rms.RecordEnumeration;
import javax.microedition.rms.RecordStore;
public class RMS {
public static final int Int1 = 0;//各个字段的默认数值
public static final int Int2 = 0;
public static final long Long1 = 0;
public static final String Str1 = "";
public static final String Str2 = "";
public static final String Str3 = "";
public static boolean addRecord(String name, int int1, int int2,//添加记录
long long1, String str1, String str2, String str3, boolean b) {
boolean success = false;
try {
RecordStore rs = RecordStore.openRecordStore(name, true);
Appointment app = new Appointment(int1, int2, long1, str1, str2,str3, b);
//既然str1作为保留字段，我们在这里就要如此操作：例如int1为我们设定的关键字，那么str1 = Integer.toString(int1);
byte[] data = app.toBytes();
rs.addRecord(data, 0, data.length);
rs.closeRecordStore();
success = true;
} catch (Exception e) {
e.printStackTrace();
}
return success;
}
public static int getNumOfRecords(String name) {//得到RMS中记录的条数
try {
RecordStore rs = RecordStore.openRecordStore(name, true);
return rs.getNumRecords();
} catch (Exception e) {
return 0;
}
}
public static Appointment[] getRecords(String name) {//取得RMS中的所有记录
Appointment[] result = { };
try {
RecordStore rs = RecordStore.openRecordStore(name, false);
RecordEnumeration re = rs.enumerateRecords(null, null, false);
result = new Appointment[rs.getNumRecords()];
for (int i = 0; i < result.length; i++) {
int j = re.previousRecordId();
Appointment app = new Appointment(rs.getRecord(j));
result = app;
//System.out.println("app["+i+"] "+app.getStr2());
}
rs.closeRecordStore();
} catch (Exception e) {
}
return result;
}
public static Appointment getRecord(String name, int j) {//根据记录编号(参数 int j)取得一条记录
Appointment result = new Appointment();
try {
RecordStore rs = RecordStore.openRecordStore(name, false);
RecordEnumeration re = rs.enumerateRecords(null, null, false);
result = new Appointment(rs.getRecord(j));
rs.closeRecordStore();
} catch (Exception e) {
}
return result;
}
public static int getIndex(String name, String content) {//得到记录号int j，这里需要使用保留字段str1
RecordStore rs = null;
RecordEnumeration re = null;
try {
rs = RecordStore.openRecordStore(name, false); //open
re = rs.enumerateRecords(null, null, false); //enumeration
for (int i = 0; i < RMS.getNumOfRecords(name); i++) {
int j = re.nextRecordId();
Appointment app = new Appointment(rs.getRecord(j));
if (app.getStr1().equals(content)) {
return j;
}
}
} catch (Exception e) {
}
return 1;
}
public static boolean setRecord(String name, int id, int int1, int int2,//设置记录号为id的记录
long long1, String str1, String str2, String str3, boolean b) {
boolean success = false;
RecordStore rs = null;
RecordEnumeration re = null;
try {
rs = RecordStore.openRecordStore(name, false); //open
re = rs.enumerateRecords(null, null, false); //enumeration
Appointment app = new Appointment(int1, int2, long1, str1, str2, str3, b);
//str1作为保留字段，在这里如此操作：例如若int1为我们设定的关键字，那么str1 = Integer.toString(int1);
byte[] data = app.toBytes();
rs.setRecord(id, data, 0, data.length);
success = true;
rs.closeRecordStore();
} catch (Exception e) {
}
return success;
}
}
import javax.microedition.rms.RecordEnumeration;
import javax.microedition.rms.RecordStore;
public class RMS {
public static final int Int1 = 0;//各个字段的默认数值
public static final int Int2 = 0;
public static final long Long1 = 0;
public static final String Str1 = "";
public static final String Str2 = "";
public static final String Str3 = "";
public static boolean addRecord(String name, int int1, int int2,//添加记录
long long1, String str1, String str2, String str3, boolean b) {
boolean success = false;
try {
RecordStore rs = RecordStore.openRecordStore(name, true);
Appointment app = new Appointment(int1, int2, long1, str1, str2,str3, b);
//既然str1作为保留字段，我们在这里就要如此操作：例如int1为我们设定的关键字，那么str1 = Integer.toString(int1);
byte[] data = app.toBytes();
rs.addRecord(data, 0, data.length);
rs.closeRecordStore();
success = true;
} catch (Exception e) {
e.printStackTrace();
}
return success;
}
public static int getNumOfRecords(String name) {//得到RMS中记录的条数
try {
RecordStore rs = RecordStore.openRecordStore(name, true);
return rs.getNumRecords();
} catch (Exception e) {
return 0;
}
}
public static Appointment[] getRecords(String name) {//取得RMS中的所有记录
Appointment[] result = { };
try {
RecordStore rs = RecordStore.openRecordStore(name, false);
RecordEnumeration re = rs.enumerateRecords(null, null, false);
result = new Appointment[rs.getNumRecords()];
for (int i = 0; i < result.length; i++) {
int j = re.previousRecordId();
Appointment app = new Appointment(rs.getRecord(j));
result = app;
//System.out.println("app["+i+"] "+app.getStr2());
}
rs.closeRecordStore();
} catch (Exception e) {
}
return result;
}
public static Appointment getRecord(String name, int j) {//根据记录编号(参数 int j)取得一条记录
Appointment result = new Appointment();
try {
RecordStore rs = RecordStore.openRecordStore(name, false);
RecordEnumeration re = rs.enumerateRecords(null, null, false);
result = new Appointment(rs.getRecord(j));
rs.closeRecordStore();
} catch (Exception e) {
}
return result;
}
public static int getIndex(String name, String content) {//得到记录号int j，这里需要使用保留字段str1
RecordStore rs = null;
RecordEnumeration re = null;
try {
rs = RecordStore.openRecordStore(name, false); //open
re = rs.enumerateRecords(null, null, false); //enumeration
for (int i = 0; i < RMS.getNumOfRecords(name); i++) {
int j = re.nextRecordId();
Appointment app = new Appointment(rs.getRecord(j));
if (app.getStr1().equals(content)) {
return j;
}
}
} catch (Exception e) {
}
return 1;
}
public static boolean setRecord(String name, int id, int int1, int int2,//设置记录号为id的记录
long long1, String str1, String str2, String str3, boolean b) {
boolean success = false;
RecordStore rs = null;
RecordEnumeration re = null;
try {
rs = RecordStore.openRecordStore(name, false); //open
re = rs.enumerateRecords(null, null, false); //enumeration
Appointment app = new Appointment(int1, int2, long1, str1, str2, str3, b);
//str1作为保留字段，在这里如此操作：例如若int1为我们设定的关键字，那么str1 = Integer.toString(int1);
byte[] data = app.toBytes();
rs.setRecord(id, data, 0, data.length);
success = true;
rs.closeRecordStore();
} catch (Exception e) {
}
return success;
}
}
在这个类中，我没有将各个Exception向外抛出，一般来说这样作是不合适的，它违背了Java的异常处理机制。但是在我使用这个类的各个J2ME程序中，它是可以胜任的，所以也就没有进行进一步的修改。
有了以上的两个类和你对RMS的理解，在程序中，你就可以顺畅的使用RMS了。
比如在MIDlet开始时，如下操作(增加记录)：
protected void startApp() throws MIDletStateChangeException {
if (RMS.getNumOfRecords(rsName) = = 0) {//rsName在前面已经声明了。String rsName=“MyRMS”;
for (int i = 0; i < 6; i++) {
RMS.addRecord(rsName, RMS.Int1, i, RMS.Long1, Integer . toString(i), RMS.Str2, "1234567890123456789",false);
}
}它就在RMS中增加了6条记录，其中int1，long1，str2，WroteFlag都没有使用，我们只是使用int2，str1(作为保留字段)和str3。
}
if (RMS.getNumOfRecords(rsName) = = 0) {//rsName在前面已经声明了。String rsName=“MyRMS”;
for (int i = 0; i < 6; i++) {
RMS.addRecord(rsName, RMS.Int1, i, RMS.Long1, Integer . toString(i), RMS.Str2, "1234567890123456789",false);
}
}它就在RMS中增加了6条记录，其中int1，long1，str2，WroteFlag都没有使用，我们只是使用int2，str1(作为保留字段)和str3。
}
