org.apache.struts2.components
Class Component

java.lang.Object
  org.apache.struts2.components.Component

Direct Known Subclasses:

ContextBean, Else, ElseIf, I18n, If, Include, OptGroup, Param, Property, Push, UIBean

public class Component
extends Object

Base class to extend for UI components.

This class is a good extension point when building reuseable UI components.

Field Summary

protected ActionMapper	actionMapper
static String	COMPONENT_STACK
protected Map	parameters
protected ValueStack	stack

Constructor Summary

Component(ValueStack stack)
Constructor.

Method Summary

void	addAllParameters(Map params) Adds all the given parameters to this component's own parameters.
void	addParameter(String key, Object value) Adds the given key and value to this component's own parameter.
boolean	altSyntax() Is the altSyntax enabled? [TRUE] See struts.properties where the altSyntax flag is defined.
void	copyParams(Map params) Pushes this component's parameter Map as well as the component itself on to the stack and then copies the supplied parameters over.
protected String	determineActionURL(String action, String namespace, String method, HttpServletRequest req, HttpServletResponse res, Map parameters, String scheme, boolean includeContext, boolean encodeResult, boolean forceAddSchemeHostAndPort, boolean escapeAmp) Renders an action URL by consulting the ActionMapper.
protected String	determineNamespace(String namespace, ValueStack stack, HttpServletRequest req) Determines the namespace of the current page being renderdd.
boolean	end(Writer writer, String body) Callback for the end tag of this component.
protected boolean	end(Writer writer, String body, boolean popComponentStack) Callback for the start tag of this component.
protected StrutsException	fieldError(String field, String errorMsg, Exception e) Constructs a RuntimeException based on the given information.
protected Component	findAncestor(Class clazz) Finds the nearest ancestor of this component stack.
protected String	findString(String expr) Evaluates the OGNL stack to find a String value.
protected String	findString(String expr, String field, String errorMsg) Evaluates the OGNL stack to find a String value.
protected Object	findValue(String expr) Finds a value from the OGNL stack based on the given expression.
protected Object	findValue(String expr, Class toType) Evaluates the OGNL stack to find an Object of the given type.
protected Object	findValue(String expr, String field, String errorMsg) Evaluates the OGNL stack to find an Object value.
private String	getComponentName() Gets the name of this component.
Stack	getComponentStack() Gets the component stack of this component.
Map	getParameters() Gets the parameters.
ValueStack	getStack() Gets the OGNL value stack assoicated with this component.
protected void	popComponentStack() Pops the component stack.
void	setActionMapper(ActionMapper mapper)
boolean	start(Writer writer) Callback for the start tag of this component.
protected String	toString(Throwable t) Constructs a string representation of the given exception.
boolean	usesBody() Overwrite to set if body shold be used.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

COMPONENT_STACK

public static final String COMPONENT_STACK

See Also:

Constant Field Values

stack

protected ValueStack stack

parameters

protected Map parameters

actionMapper

protected ActionMapper actionMapper

Constructor Detail

Component

public Component(ValueStack stack)

Constructor.

Parameters:

stack - OGNL value stack.

Method Detail

getComponentName

private String getComponentName()

Gets the name of this component.

Returns:

the name of this component.

setActionMapper

public void setActionMapper(ActionMapper mapper)

getStack

public ValueStack getStack()

Gets the OGNL value stack assoicated with this component.

Returns:

the OGNL value stack assoicated with this component.

getComponentStack

public Stack getComponentStack()

Gets the component stack of this component.

Returns:

the component stack of this component, never null.

start

public boolean start(Writer writer)

Callback for the start tag of this component. Should the body be evaluated?

Parameters:

writer - the output writer.

Returns:

true if the body should be evaluated

end

public boolean end(Writer writer,
                   String body)

Callback for the end tag of this component. Should the body be evaluated again?

NOTE: will pop component stack.

Parameters:

writer - the output writer.

body - the rendered body.

Returns:

true if the body should be evaluated again

end

protected boolean end(Writer writer,
                      String body,
                      boolean popComponentStack)

Callback for the start tag of this component. Should the body be evaluated again?

NOTE: has a parameter to determine to pop the component stack.

Parameters:

writer - the output writer.

body - the rendered body.

popComponentStack - should the component stack be popped?

Returns:

true if the body should be evaluated again

popComponentStack

protected void popComponentStack()

Pops the component stack.

findAncestor

protected Component findAncestor(Class clazz)

Finds the nearest ancestor of this component stack.

Parameters:

clazz - the class to look for, or if assignable from.

Returns:

the component if found, null if not.

findString

protected String findString(String expr)

Evaluates the OGNL stack to find a String value.

Parameters:

expr - OGNL expression.

Returns:

the String value found.

findString

protected String findString(String expr,
                            String field,
                            String errorMsg)

Evaluates the OGNL stack to find a String value.

If the given expression is null a error is logged and a RuntimeException is thrown constructed with a messaged based on the given field and errorMsg paramter.

Parameters:

expr - OGNL expression.

field - field name used when throwing RuntimeException.

errorMsg - error message used when throwing RuntimeException.

Returns:

the String value found.

Throws:

StrutsException - is thrown in case of expression is null.

fieldError

protected StrutsException fieldError(String field,
                                     String errorMsg,
                                     Exception e)

Constructs a RuntimeException based on the given information.

A message is constructed and logged at ERROR level before being returned as a RuntimeException.

Parameters:

field - field name used when throwing RuntimeException.

errorMsg - error message used when throwing RuntimeException.

e - the caused exception, can be null.

Returns:

the constructed StrutsException.

findValue

protected Object findValue(String expr)

Finds a value from the OGNL stack based on the given expression. Will always evaluate expr against stack except when expr is null. If altsyntax (%{...}) is applied, simply strip it off.

Parameters:

expr - the expression. Returns null if expr is null.

Returns:

the value, null if not found.

altSyntax

public boolean altSyntax()

Is the altSyntax enabled? [TRUE]

See struts.properties where the altSyntax flag is defined.

findValue

protected Object findValue(String expr,
                           String field,
                           String errorMsg)

Evaluates the OGNL stack to find an Object value.

Function just like findValue(String) except that if the given expression is null a error is logged and a RuntimeException is thrown constructed with a messaged based on the given field and errorMsg paramter.

Parameters:

expr - OGNL expression.

field - field name used when throwing RuntimeException.

errorMsg - error message used when throwing RuntimeException.

Returns:

the Object found, is never null.

Throws:

StrutsException - is thrown in case of not found in the OGNL stack, or expression is null.

findValue

protected Object findValue(String expr,
                           Class toType)

Evaluates the OGNL stack to find an Object of the given type. Will evaluate expr the portion wrapped with altSyntax (%{...}) against stack when altSyntax is on, else the whole expr is evaluated against the stack.

This method only supports the altSyntax. So this should be set to true.

Parameters:

expr - OGNL expression.

toType - the type expected to find.

Returns:

the Object found, or null if not found.

determineActionURL

protected String determineActionURL(String action,
                                    String namespace,
                                    String method,
                                    HttpServletRequest req,
                                    HttpServletResponse res,
                                    Map parameters,
                                    String scheme,
                                    boolean includeContext,
                                    boolean encodeResult,
                                    boolean forceAddSchemeHostAndPort,
                                    boolean escapeAmp)

Renders an action URL by consulting the ActionMapper.

Parameters:

action - the action

namespace - the namespace

method - the method

req - HTTP request

res - HTTP response

parameters - parameters

scheme - http or https

includeContext - should the context path be included or not

encodeResult - should the url be encoded

forceAddSchemeHostAndPort - should the scheme host and port be forced

escapeAmp - should ampersand (&) be escaped to &

Returns:

the action url.

determineNamespace

protected String determineNamespace(String namespace,
                                    ValueStack stack,
                                    HttpServletRequest req)

Determines the namespace of the current page being renderdd. Useful for Form, URL, and href generations.

Parameters:

namespace - the namespace

stack - OGNL value stack

req - HTTP request

Returns:

the namepsace of the current page being rendered, is never null.

copyParams

public void copyParams(Map params)

Pushes this component's parameter Map as well as the component itself on to the stack and then copies the supplied parameters over. Because the component's parameter Map is pushed before the component itself, any key-value pair that can't be assigned to componet will be set in the parameters Map.

Parameters:

params - the parameters to copy.

toString

protected String toString(Throwable t)

Constructs a string representation of the given exception.

Parameters:

t - the exception

Returns:

the exception as a string.

getParameters

public Map getParameters()

Gets the parameters.

Returns:

the parameters. Is never null.

addAllParameters

public void addAllParameters(Map params)

Adds all the given parameters to this component's own parameters.

Parameters:

params - the parameters to add.

addParameter

public void addParameter(String key,
                         Object value)

Adds the given key and value to this component's own parameter.

If the provided key is null nothing happens. If the provided value is null any existing parameter with the given key name is removed.

Parameters:

key - the key of the new parameter to add.

value - the value assoicated with the key.

usesBody

public boolean usesBody()

Overwrite to set if body shold be used.

Returns:

always false for this component.