ItemSpawner Bug

[Server thread/ERROR]: Could not load 'plugins\ItemSpawner.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NoClassDefFoundError: net/minecraft/server/v1_7_R3/World
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:133) ~[spigot.jar:git-Spigot-1551]
	at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:329) ~[spigot.jar:git-Spigot-1551]
	at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [spigot.jar:git-Spigot-1551]
	at org.bukkit.craftbukkit.v1_7_R4.CraftServer.loadPlugins(CraftServer.java:369) [spigot.jar:git-Spigot-1551]
	at net.minecraft.server.v1_7_R4.DedicatedServer.init(DedicatedServer.java:152) [spigot.jar:git-Spigot-1551]
	at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:458) [spigot.jar:git-Spigot-1551]
	at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [spigot.jar:git-Spigot-1551]
Caused by: java.lang.NoClassDefFoundError: net/minecraft/server/v1_7_R3/World
	at java.lang.Class.forName0(Native Method) ~[?:1.8.0_05]
	at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_05]
	at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[spigot.jar:git-Spigot-1551]
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[spigot.jar:git-Spigot-1551]
	... 6 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_7_R3.World
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:67) ~[spigot.jar:git-Spigot-1551]
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[spigot.jar:git-Spigot-1551]
	at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_05]
	at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_05]
	at java.lang.Class.forName0(Native Method) ~[?:1.8.0_05]
	at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_05]
	at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[spigot.jar:git-Spigot-1551]
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[spigot.jar:git-Spigot-1551]
	... 6 more