How can I emulate 1.7.10's adventure mode in 1.8?

Create an entitydata command that will edit your inventory. The only thing it will change is add this tag to all items in the inventory: CanPlaceOn:["minecraft:stone","minecraft:grass_block","minecraft:dirt"... putting all block IDs on. Then create an array of command blocks facing upwards. The bottom layer will be repeating command blocks with: clear @p TOOLNAME 0 1 The top layer will be chain conditional command blocks with command: give @p TOOLNAME 1 1 {CanDestroy:[in this box you put all blocks you want the tool to break]}

This will take a while. But once you are done upload map to the internet and enjoy adventure-loving people wanting to play on it!

Add the CanBreak or CanPlaceOn tag to items.

Example:

/give @p minecraft:stone 1 0 {CanPlaceOn:["minecraft:dirt"]} This would give the closest player a stone block that you can place on dirt.

/give @p minecraft:stone_sword 1 0 {CanDestroy:["minecraft:web"]} And this would give a stone sword that can destroy webs.

You could solve half the problem by switching between survival and adventure mode based on the item you are holding. However, you would still need CanBreak tags on all your tools. (Also you could break blocks when holding another block or nothing)

This is only a partwise solution, as this allows you to place blocks only when you are not holding a tool.

There are 2 ways to do this, both take HOURS of prep time.

1) go on survival mode, not adventure do a command block on a clock saying

/effect @p minecraft:mining_fatigue 10 100 true

place a string of command blocks with this command:

/clear @p wooden_axeBLOCKID0 with a comparator, immediately followed by a repeater

for every tool and BLOCK ID (damage) for tool.

then make it so that if ANY of the repeaters are on do /effect @a clear

2) You could create a scoreboard objective for crafting every tool, eg:

/scoreboard objectives craftWoodenAxe stat.craftItem.minecraft.stone_axe

create a redstone-block-clock facing +X, and with command blocks from lowest to highest X value do this:

/clear @a[score_craftWoodenAxe_min=1] wooden_axe 0

/give @a [score_craftWoodenAxe_min=1] wooden_axe 1 {CanBreak:["PUT A BLOCK","PUT A BLOCK","etc"]}

/scoreboard players remove @p[score_craftWoodenAxe_min=1] craftWoodenAxe 1

for every tool...

You would probaly be better off waiting to see if mojang adds this later.