[Javassist user questions] - Problem with branches and ldc/ldc_w
by tumbleweed
Hello,
i'm working with javassist for quite some time now and I must say it is really impressive what this thing can do, and with what ease!
Anyways, I'm confronted with one problem:
My tool inserts an arbitrary series of conditional branches and some code afterwards. This means I have to precalculate the number of bytes inserted for all following conditions and the code in respect to set the branch offset. All works well unless I load a string constant using addLdc(String). In this case I am unable to precalculate whether there are 3 bytes (ldc) or 4 bytes (ldc_w) inserted, since this depends on the ConstTables state at insertion time.
I've developed a workaround for my case by extending the Bytecode class and altering its behaviour with
| private ArrayList<Integer> m_branches;
| ...
|
| public void addBranch(int code, int branchOffset) {
| // branch opcode is inserted at offset getSize()
| m_branches.add(getSize());
| addOpcode(code);
| add16bit(branchOffset);
| }
|
| private void adjustBranches(int end, int shift) {
| for (Integer pos : m_branches) {
| int branchOffset = read16bit(pos + 1);
| if ((pos + branchOffset) <= end) continue;
| write16bit(pos + 1, branchOffset + shift);
| }
| }
|
| @Override
| public void addLdc(int i) {
| if (i > 0xFF) {
| adjustBranches(getSize(), 1);
| addOpcode(LDC_W);
| addIndex(i);
| } else {
| addOpcode(LDC);
| add(i);
| }
| }
|
I think this is could be extended to a general solution, if it would be well defined how many bytes one should asume to be inserted.
Is there a way around this problem that I've overseen or is this really a "bug"?
---
By the way, is there any reason there is no
| public void add16bit(int value) {
| value = value % 65536;
| add(value >> 8);
| add(value % 256);
| }
|
defined in Bytecode? Since it is required for inserting branch offsets...
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17 years
[JBoss Portal] - Re: Configure Portlet-Instances
by matallen
If you configure your portlet-instance.xml like this:
<?xml version="1.0" standalone="yes"?>
| <deployments>
| <deployment>
| <instance>
| <instance-id>XPortletInstance</instance-id>
| <portlet-ref>XPortlet</portlet-ref>
| <preferences>
| <preference>
| <name>name</name>
| <value>X-Portlet</value>
| </preference>
| </preferences>
| <security-constraint>
| <policy-permission>
| <action-name>admin</action-name>
| <role-name>role1</role-name>
| </policy-permission>
| </security-constraint>
| </instance>
| </deployment>
| <deployment>
| <instance>
| <instance-id>YPortletInstance</instance-id>
| <portlet-ref>YPortlet</portlet-ref>
| <preferences>
| <preference>
| <name>name</name>
| <value>Y-Portlet</value>
| </preference>
| </preferences>
| <security-constraint>
| <policy-permission>
| <action-name>admin</action-name>
| <role-name>role1</role-name>
| </policy-permission>
| </security-constraint>
| </instance>
| </deployment>
| </deployments>
then you can retrieve the values within your portlet with this code:
renderRequest.getPreferences().getValue("name", "default_name");
and thus, make your X portlet act differentlyto your Y portlet instance accordingly
Hope this helps,
Mat
View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4243336#4243336
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17 years
