Eclipse Cookbook

5.11. Creating Field, Method, and Exception Breakpoints

Problem

You need to stop execution when a field or method is about to be accessed, or when a certain exception occurs.

Solution

Set a field, method, or exception breakpoint using the appropriate items in the Run menu.

Discussion

The standard breakpoints we’ve been using are called line breakpoints; besides line breakpoints, the JDT supports three other types of breakpoints: field, method, and exception breakpoints.

Field breakpoints

Field breakpoints, also called watchpoints, suspend execution when your code is going to access and/or modify the value of a field (watchpoints cannot be set on local variables, only on fields). This is different from when you set a condition on a standard breakpoint; this breakpoint happens every time a field is going to be accessed in any way. Using a watchpoint is often much easier than trying to catch all the possible points in your code in which the field you want to watch might be modified.

To set a watchpoint, highlight a field in a Java view and select Run→ Add/Remove Watchpoint. The new watchpoint will appear in the Breakpoints view, and you can configure it by right-clicking it and then clicking Breakpoint Properties, which opens the Java Watchpoint Properties dialog shown in Figure 5-18. Note in particular that you can check two checkboxes here—“Access” and “Modification”—that enable you to indicate whether you want to suspend execution when the field is accessed and/or when it is modified. ...