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.IOException;
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8 | import java.nio.charset.StandardCharsets;
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9 | import java.nio.file.Files;
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10 | import java.nio.file.InvalidPathException;
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11 | import java.util.concurrent.TimeUnit;
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12 |
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13 | import org.openstreetmap.josm.spi.preferences.Config;
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14 | import org.openstreetmap.josm.tools.Logging;
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15 | import org.openstreetmap.josm.tools.Utils;
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16 |
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17 | /**
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18 | * Use this class if you want to cache and store a single file that gets updated regularly.
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19 | * Unless you flush() it will be kept in memory. If you want to cache a lot of data and/or files, use CacheFiles.
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20 | * @author xeen
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21 | * @param <T> a {@link Throwable} that may be thrown during {@link #updateData()},
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22 | * use {@link RuntimeException} if no exception must be handled.
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23 | * @since 1450
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24 | */
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25 | public abstract class CacheCustomContent<T extends Throwable> {
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26 |
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27 | /** Update interval meaning an update is always needed */
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28 | public static final int INTERVAL_ALWAYS = -1;
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29 | /** Update interval meaning an update is needed each hour */
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30 | public static final int INTERVAL_HOURLY = (int) TimeUnit.HOURS.toSeconds(1);
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31 | /** Update interval meaning an update is needed each day */
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32 | public static final int INTERVAL_DAILY = (int) TimeUnit.DAYS.toSeconds(1);
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33 | /** Update interval meaning an update is needed each week */
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34 | public static final int INTERVAL_WEEKLY = (int) TimeUnit.DAYS.toSeconds(7);
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35 | /** Update interval meaning an update is needed each month */
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36 | public static final int INTERVAL_MONTHLY = (int) TimeUnit.DAYS.toSeconds(28);
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37 | /** Update interval meaning an update is never needed */
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38 | public static final int INTERVAL_NEVER = Integer.MAX_VALUE;
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39 |
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40 | /**
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41 | * Where the data will be stored
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42 | */
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43 | private byte[] data;
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44 |
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45 | /**
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46 | * The ident that identifies the stored file. Includes file-ending.
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47 | */
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48 | private final String ident;
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49 |
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50 | /**
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51 | * The (file-)path where the data will be stored
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52 | */
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53 | private final File path;
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54 |
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55 | /**
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56 | * How often to update the cached version
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57 | */
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58 | private final int updateInterval;
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59 |
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60 | /**
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61 | * This function will be executed when an update is required. It has to be implemented by the
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62 | * inheriting class and should use a worker if it has a long wall time as the function is
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63 | * executed in the current thread.
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64 | * @return the data to cache
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65 | * @throws T a {@link Throwable}
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66 | */
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67 | protected abstract byte[] updateData() throws T;
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68 |
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69 | /**
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70 | * Initializes the class. Note that all read data will be stored in memory until it is flushed
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71 | * by flushData().
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72 | * @param ident ident that identifies the stored file. Includes file-ending.
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73 | * @param updateInterval update interval in seconds. -1 means always
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74 | */
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75 | public CacheCustomContent(String ident, int updateInterval) {
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76 | this.ident = ident;
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77 | this.updateInterval = updateInterval;
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78 | this.path = new File(Config.getDirs().getCacheDirectory(true), ident);
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79 | }
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80 |
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81 | /**
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82 | * This function serves as a comfort hook to perform additional checks if the cache is valid
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83 | * @return True if the cached copy is still valid
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84 | */
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85 | protected boolean isCacheValid() {
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86 | return true;
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87 | }
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88 |
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89 | private boolean needsUpdate() {
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90 | if (isOffline()) {
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91 | return false;
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92 | }
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93 | return Config.getPref().getInt("cache." + ident, 0) + updateInterval < TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis())
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94 | || !isCacheValid();
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95 | }
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96 |
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97 | private boolean isOffline() {
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98 | try {
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99 | checkOfflineAccess();
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100 | return false;
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101 | } catch (OfflineAccessException e) {
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102 | Logging.trace(e);
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103 | return true;
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104 | }
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105 | }
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106 |
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107 | /**
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108 | * Ensures underlying resource is not accessed in offline mode.
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109 | * @throws OfflineAccessException if resource is accessed in offline mode
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110 | */
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111 | protected abstract void checkOfflineAccess();
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112 |
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113 | /**
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114 | * Updates data if required
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115 | * @return Returns the data
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116 | * @throws T if an error occurs
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117 | */
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118 | public byte[] updateIfRequired() throws T {
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119 | if (needsUpdate())
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120 | return updateForce();
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121 | return getData();
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122 | }
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123 |
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124 | /**
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125 | * Updates data if required
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126 | * @return Returns the data as string
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127 | * @throws T if an error occurs
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128 | */
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129 | public String updateIfRequiredString() throws T {
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130 | if (needsUpdate())
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131 | return updateForceString();
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132 | return getDataString();
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133 | }
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134 |
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135 | /**
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136 | * Executes an update regardless of updateInterval
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137 | * @return Returns the data
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138 | * @throws T if an error occurs
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139 | */
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140 | private byte[] updateForce() throws T {
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141 | this.data = updateData();
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142 | saveToDisk();
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143 | Config.getPref().putInt("cache." + ident, (int) (TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis())));
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144 | return data;
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145 | }
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146 |
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147 | /**
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148 | * Executes an update regardless of updateInterval
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149 | * @return Returns the data as String
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150 | * @throws T if an error occurs
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151 | */
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152 | public String updateForceString() throws T {
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153 | updateForce();
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154 | return new String(data, StandardCharsets.UTF_8);
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155 | }
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156 |
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157 | /**
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158 | * Returns the data without performing any updates
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159 | * @return the data
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160 | * @throws T if an error occurs
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161 | */
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162 | public byte[] getData() throws T {
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163 | if (data == null) {
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164 | loadFromDisk();
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165 | }
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166 | return Utils.copyArray(data);
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167 | }
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168 |
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169 | /**
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170 | * Returns the data without performing any updates
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171 | * @return the data as String
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172 | * @throws T if an error occurs
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173 | */
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174 | public String getDataString() throws T {
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175 | byte[] array = getData();
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176 | if (array == null) {
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177 | return null;
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178 | }
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179 | return new String(array, StandardCharsets.UTF_8);
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180 | }
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181 |
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182 | /**
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183 | * Tries to load the data using the given ident from disk. If this fails, data will be updated, unless run in offline mode
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184 | * @throws T a {@link Throwable}
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185 | */
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186 | private void loadFromDisk() throws T {
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187 | try (BufferedInputStream input = new BufferedInputStream(Files.newInputStream(path.toPath()))) {
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188 | this.data = new byte[input.available()];
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189 | if (input.read(this.data) < this.data.length) {
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190 | Logging.error("Failed to read expected contents from "+path);
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191 | }
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192 | } catch (IOException | InvalidPathException e) {
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193 | Logging.trace(e);
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194 | if (!isOffline()) {
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195 | this.data = updateForce();
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196 | }
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197 | }
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198 | }
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199 |
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200 | /**
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201 | * Stores the data to disk
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202 | */
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203 | private void saveToDisk() {
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204 | try (BufferedOutputStream output = new BufferedOutputStream(Files.newOutputStream(path.toPath()))) {
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205 | output.write(this.data);
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206 | output.flush();
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207 | } catch (IOException | InvalidPathException | SecurityException e) {
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208 | Logging.log(Logging.LEVEL_ERROR, "Unable to save data", e);
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209 | }
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210 | }
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211 |
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212 | /**
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213 | * Flushes the data from memory. Class automatically reloads it from disk or updateData() if required
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214 | */
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215 | public void flushData() {
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216 | data = null;
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217 | }
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218 | }
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