1 | // License: GPL. For details, see LICENSE file.
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2 | package org.openstreetmap.josm.io;
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3 |
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4 | import java.io.BufferedInputStream;
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5 | import java.io.BufferedOutputStream;
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6 | import java.io.File;
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7 | import java.io.FileInputStream;
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8 | import java.io.FileOutputStream;
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9 | import java.io.IOException;
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10 | import java.io.UnsupportedEncodingException;
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11 | import java.util.Date;
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12 |
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13 | import org.openstreetmap.josm.Main;
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14 |
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15 | /**
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16 | * Use this class if you want to cache and store a single file that gets updated regularly.
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17 | * Unless you flush() it will be kept in memory. If you want to cache a lot of data and/or files,
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18 | * use CacheFiles
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19 | * @param <T> a {@link Throwable} that may be thrown during {@link #updateData()},
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20 | * use {@link RuntimeException} if no exception must be handled.
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21 | * @author xeen
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22 | *
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23 | */
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24 | public abstract class CacheCustomContent<T extends Throwable> {
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25 | /**
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26 | * Common intervals
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27 | */
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28 | final static public int INTERVAL_ALWAYS = -1;
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29 | final static public int INTERVAL_HOURLY = 60*60;
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30 | final static public int INTERVAL_DAILY = INTERVAL_HOURLY * 24;
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31 | final static public int INTERVAL_WEEKLY = INTERVAL_DAILY * 7;
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32 | final static public int INTERVAL_MONTHLY = INTERVAL_WEEKLY * 4;
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33 | final static public int INTERVAL_NEVER = Integer.MAX_VALUE;
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34 |
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35 | /**
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36 | * Where the data will be stored
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37 | */
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38 | private byte[] data = null;
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39 |
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40 | /**
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41 | * The ident that identifies the stored file. Includes file-ending.
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42 | */
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43 | final private String ident;
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44 |
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45 | /**
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46 | * The (file-)path where the data will be stored
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47 | */
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48 | final private File path;
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49 |
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50 | /**
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51 | * How often to update the cached version
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52 | */
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53 | final private int updateInterval;
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54 |
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55 | /**
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56 | * This function will be executed when an update is required. It has to be implemented by the
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57 | * inheriting class and should use a worker if it has a long wall time as the function is
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58 | * executed in the current thread.
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59 | * @return the data to cache
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60 | */
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61 | protected abstract byte[] updateData() throws T;
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62 |
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63 | /**
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64 | * This function serves as a comfort hook to perform additional checks if the cache is valid
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65 | * @return True if the cached copy is still valid
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66 | */
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67 | protected boolean isCacheValid() {
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68 | return true;
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69 | }
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70 |
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71 | /**
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72 | * Initializes the class. Note that all read data will be stored in memory until it is flushed
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73 | * by flushData().
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74 | * @param ident
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75 | * @param updateInterval
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76 | */
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77 | public CacheCustomContent(String ident, int updateInterval) {
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78 | this.ident = ident;
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79 | this.updateInterval = updateInterval;
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80 | this.path = new File(Main.pref.getCacheDirectory(), ident);
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81 | }
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82 |
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83 | /**
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84 | * Updates data if required
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85 | * @return Returns the data
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86 | */
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87 | public byte[] updateIfRequired() throws T {
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88 | if (Main.pref.getInteger("cache." + ident, 0) + updateInterval < new Date().getTime()/1000
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89 | || !isCacheValid())
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90 | return updateForce();
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91 | return getData();
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92 | }
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93 |
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94 | /**
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95 | * Updates data if required
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96 | * @return Returns the data as string
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97 | */
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98 | public String updateIfRequiredString() throws T {
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99 | if (Main.pref.getInteger("cache." + ident, 0) + updateInterval < new Date().getTime()/1000
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100 | || !isCacheValid())
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101 | return updateForceString();
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102 | return getDataString();
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103 | }
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104 |
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105 | /**
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106 | * Executes an update regardless of updateInterval
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107 | * @return Returns the data
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108 | */
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109 | public byte[] updateForce() throws T {
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110 | this.data = updateData();
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111 | saveToDisk();
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112 | Main.pref.putInteger("cache." + ident, (int)(new Date().getTime()/1000));
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113 | return data;
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114 | }
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115 |
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116 | /**
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117 | * Executes an update regardless of updateInterval
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118 | * @return Returns the data as String
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119 | */
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120 | public String updateForceString() throws T {
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121 | updateForce();
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122 | try {
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123 | return new String(data, "utf-8");
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124 | } catch (UnsupportedEncodingException e){
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125 | e.printStackTrace();
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126 | return "";
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127 | }
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128 | }
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129 |
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130 | /**
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131 | * Returns the data without performing any updates
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132 | * @return the data
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133 | */
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134 | public byte[] getData() throws T {
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135 | if (data == null) {
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136 | loadFromDisk();
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137 | }
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138 | return data;
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139 | }
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140 |
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141 | /**
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142 | * Returns the data without performing any updates
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143 | * @return the data as String
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144 | */
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145 | public String getDataString() throws T {
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146 | try {
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147 | return new String(getData(), "utf-8");
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148 | } catch(UnsupportedEncodingException e){
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149 | e.printStackTrace();
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150 | return "";
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151 | }
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152 | }
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153 |
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154 | /**
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155 | * Tries to load the data using the given ident from disk. If this fails, data will be updated
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156 | */
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157 | private void loadFromDisk() throws T {
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158 | if (Main.applet)
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159 | this.data = updateForce();
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160 | else {
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161 | try {
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162 | BufferedInputStream input = new BufferedInputStream(new FileInputStream(path));
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163 | this.data = new byte[input.available()];
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164 | input.read(this.data);
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165 | input.close();
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166 | } catch (IOException e) {
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167 | this.data = updateForce();
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168 | }
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169 | }
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170 | }
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171 |
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172 | /**
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173 | * Stores the data to disk
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174 | */
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175 | private void saveToDisk() {
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176 | if (Main.applet)
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177 | return;
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178 | try {
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179 | BufferedOutputStream output = new BufferedOutputStream(new FileOutputStream(path));
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180 | output.write(this.data);
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181 | output.flush();
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182 | output.close();
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183 | } catch(Exception e) {
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184 | e.printStackTrace();
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185 | }
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186 | }
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187 |
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188 | /**
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189 | * Flushes the data from memory. Class automatically reloads it from disk or updateData() if
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190 | * required
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191 | */
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192 | public void flushData() {
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193 | data = null;
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194 | }
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195 | }
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